1 \input texinfo @c -*-Texinfo-*-
2 @c Copyright (C) 1991-2014 Free Software Foundation, Inc.
3 @c UPDATE!! On future updates--
4 @c (1) check for new machine-dep cmdline options in
5 @c md_parse_option definitions in config/tc-*.c
6 @c (2) for platform-specific directives, examine md_pseudo_op
8 @c (3) for object-format specific directives, examine obj_pseudo_op
10 @c (4) portable directives in potable[] in read.c
14 @macro gcctabopt{body}
17 @c defaults, config file may override:
22 @include asconfig.texi
27 @c common OR combinations of conditions
53 @set abnormal-separator
57 @settitle Using @value{AS}
60 @settitle Using @value{AS} (@value{TARGET})
62 @setchapternewpage odd
67 @c WARE! Some of the machine-dependent sections contain tables of machine
68 @c instructions. Except in multi-column format, these tables look silly.
69 @c Unfortunately, Texinfo doesn't have a general-purpose multi-col format, so
70 @c the multi-col format is faked within @example sections.
72 @c Again unfortunately, the natural size that fits on a page, for these tables,
73 @c is different depending on whether or not smallbook is turned on.
74 @c This matters, because of order: text flow switches columns at each page
77 @c The format faked in this source works reasonably well for smallbook,
78 @c not well for the default large-page format. This manual expects that if you
79 @c turn on @smallbook, you will also uncomment the "@set SMALL" to enable the
80 @c tables in question. You can turn on one without the other at your
81 @c discretion, of course.
84 @c the insn tables look just as silly in info files regardless of smallbook,
85 @c might as well show 'em anyways.
89 @dircategory Software development
91 * As: (as). The GNU assembler.
92 * Gas: (as). The GNU assembler.
100 This file documents the GNU Assembler "@value{AS}".
102 @c man begin COPYRIGHT
103 Copyright @copyright{} 1991-2014 Free Software Foundation, Inc.
105 Permission is granted to copy, distribute and/or modify this document
106 under the terms of the GNU Free Documentation License, Version 1.3
107 or any later version published by the Free Software Foundation;
108 with no Invariant Sections, with no Front-Cover Texts, and with no
109 Back-Cover Texts. A copy of the license is included in the
110 section entitled ``GNU Free Documentation License''.
116 @title Using @value{AS}
117 @subtitle The @sc{gnu} Assembler
119 @subtitle for the @value{TARGET} family
121 @ifset VERSION_PACKAGE
123 @subtitle @value{VERSION_PACKAGE}
126 @subtitle Version @value{VERSION}
129 The Free Software Foundation Inc.@: thanks The Nice Computer
130 Company of Australia for loaning Dean Elsner to write the
131 first (Vax) version of @command{as} for Project @sc{gnu}.
132 The proprietors, management and staff of TNCCA thank FSF for
133 distracting the boss while they got some work
136 @author Dean Elsner, Jay Fenlason & friends
140 \hfill {\it Using {\tt @value{AS}}}\par
141 \hfill Edited by Cygnus Support\par
143 %"boxit" macro for figures:
144 %Modified from Knuth's ``boxit'' macro from TeXbook (answer to exercise 21.3)
145 \gdef\boxit#1#2{\vbox{\hrule\hbox{\vrule\kern3pt
146 \vbox{\parindent=0pt\parskip=0pt\hsize=#1\kern3pt\strut\hfil
147 #2\hfil\strut\kern3pt}\kern3pt\vrule}\hrule}}%box with visible outline
148 \gdef\ibox#1#2{\hbox to #1{#2\hfil}\kern8pt}% invisible box
151 @vskip 0pt plus 1filll
152 Copyright @copyright{} 1991-2014 Free Software Foundation, Inc.
154 Permission is granted to copy, distribute and/or modify this document
155 under the terms of the GNU Free Documentation License, Version 1.3
156 or any later version published by the Free Software Foundation;
157 with no Invariant Sections, with no Front-Cover Texts, and with no
158 Back-Cover Texts. A copy of the license is included in the
159 section entitled ``GNU Free Documentation License''.
166 @top Using @value{AS}
168 This file is a user guide to the @sc{gnu} assembler @command{@value{AS}}
169 @ifset VERSION_PACKAGE
170 @value{VERSION_PACKAGE}
172 version @value{VERSION}.
174 This version of the file describes @command{@value{AS}} configured to generate
175 code for @value{TARGET} architectures.
178 This document is distributed under the terms of the GNU Free
179 Documentation License. A copy of the license is included in the
180 section entitled ``GNU Free Documentation License''.
183 * Overview:: Overview
184 * Invoking:: Command-Line Options
186 * Sections:: Sections and Relocation
188 * Expressions:: Expressions
189 * Pseudo Ops:: Assembler Directives
191 * Object Attributes:: Object Attributes
193 * Machine Dependencies:: Machine Dependent Features
194 * Reporting Bugs:: Reporting Bugs
195 * Acknowledgements:: Who Did What
196 * GNU Free Documentation License:: GNU Free Documentation License
197 * AS Index:: AS Index
204 This manual is a user guide to the @sc{gnu} assembler @command{@value{AS}}.
206 This version of the manual describes @command{@value{AS}} configured to generate
207 code for @value{TARGET} architectures.
211 @cindex invocation summary
212 @cindex option summary
213 @cindex summary of options
214 Here is a brief summary of how to invoke @command{@value{AS}}. For details,
215 see @ref{Invoking,,Command-Line Options}.
217 @c man title AS the portable GNU assembler.
221 gcc(1), ld(1), and the Info entries for @file{binutils} and @file{ld}.
225 @c We don't use deffn and friends for the following because they seem
226 @c to be limited to one line for the header.
228 @c man begin SYNOPSIS
229 @value{AS} [@b{-a}[@b{cdghlns}][=@var{file}]] [@b{--alternate}] [@b{-D}]
230 [@b{--compress-debug-sections}] [@b{--nocompress-debug-sections}]
231 [@b{--debug-prefix-map} @var{old}=@var{new}]
232 [@b{--defsym} @var{sym}=@var{val}] [@b{-f}] [@b{-g}] [@b{--gstabs}]
233 [@b{--gstabs+}] [@b{--gdwarf-2}] [@b{--gdwarf-sections}]
234 [@b{--help}] [@b{-I} @var{dir}] [@b{-J}]
235 [@b{-K}] [@b{-L}] [@b{--listing-lhs-width}=@var{NUM}]
236 [@b{--listing-lhs-width2}=@var{NUM}] [@b{--listing-rhs-width}=@var{NUM}]
237 [@b{--listing-cont-lines}=@var{NUM}] [@b{--keep-locals}] [@b{-o}
238 @var{objfile}] [@b{-R}] [@b{--reduce-memory-overheads}] [@b{--statistics}]
239 [@b{-v}] [@b{-version}] [@b{--version}] [@b{-W}] [@b{--warn}]
240 [@b{--fatal-warnings}] [@b{-w}] [@b{-x}] [@b{-Z}] [@b{@@@var{FILE}}]
241 [@b{--size-check=[error|warning]}]
242 [@b{--target-help}] [@var{target-options}]
243 [@b{--}|@var{files} @dots{}]
245 @c Target dependent options are listed below. Keep the list sorted.
246 @c Add an empty line for separation.
249 @emph{Target AArch64 options:}
251 [@b{-mabi}=@var{ABI}]
255 @emph{Target Alpha options:}
257 [@b{-mdebug} | @b{-no-mdebug}]
258 [@b{-replace} | @b{-noreplace}]
259 [@b{-relax}] [@b{-g}] [@b{-G@var{size}}]
260 [@b{-F}] [@b{-32addr}]
264 @emph{Target ARC options:}
270 @emph{Target ARM options:}
271 @c Don't document the deprecated options
272 [@b{-mcpu}=@var{processor}[+@var{extension}@dots{}]]
273 [@b{-march}=@var{architecture}[+@var{extension}@dots{}]]
274 [@b{-mfpu}=@var{floating-point-format}]
275 [@b{-mfloat-abi}=@var{abi}]
276 [@b{-meabi}=@var{ver}]
279 [@b{-mapcs-32}|@b{-mapcs-26}|@b{-mapcs-float}|
280 @b{-mapcs-reentrant}]
281 [@b{-mthumb-interwork}] [@b{-k}]
285 @emph{Target Blackfin options:}
286 [@b{-mcpu}=@var{processor}[-@var{sirevision}]]
293 @emph{Target CRIS options:}
294 [@b{--underscore} | @b{--no-underscore}]
296 [@b{--emulation=criself} | @b{--emulation=crisaout}]
297 [@b{--march=v0_v10} | @b{--march=v10} | @b{--march=v32} | @b{--march=common_v10_v32}]
298 @c Deprecated -- deliberately not documented.
303 @emph{Target D10V options:}
308 @emph{Target D30V options:}
309 [@b{-O}|@b{-n}|@b{-N}]
313 @emph{Target EPIPHANY options:}
314 [@b{-mepiphany}|@b{-mepiphany16}]
318 @emph{Target H8/300 options:}
322 @c HPPA has no machine-dependent assembler options (yet).
326 @emph{Target i386 options:}
327 [@b{--32}|@b{--x32}|@b{--64}] [@b{-n}]
328 [@b{-march}=@var{CPU}[+@var{EXTENSION}@dots{}]] [@b{-mtune}=@var{CPU}]
332 @emph{Target i960 options:}
333 @c see md_parse_option in tc-i960.c
334 [@b{-ACA}|@b{-ACA_A}|@b{-ACB}|@b{-ACC}|@b{-AKA}|@b{-AKB}|
336 [@b{-b}] [@b{-no-relax}]
340 @emph{Target IA-64 options:}
341 [@b{-mconstant-gp}|@b{-mauto-pic}]
342 [@b{-milp32}|@b{-milp64}|@b{-mlp64}|@b{-mp64}]
344 [@b{-mtune=itanium1}|@b{-mtune=itanium2}]
345 [@b{-munwind-check=warning}|@b{-munwind-check=error}]
346 [@b{-mhint.b=ok}|@b{-mhint.b=warning}|@b{-mhint.b=error}]
347 [@b{-x}|@b{-xexplicit}] [@b{-xauto}] [@b{-xdebug}]
351 @emph{Target IP2K options:}
352 [@b{-mip2022}|@b{-mip2022ext}]
356 @emph{Target M32C options:}
357 [@b{-m32c}|@b{-m16c}] [-relax] [-h-tick-hex]
361 @emph{Target M32R options:}
362 [@b{--m32rx}|@b{--[no-]warn-explicit-parallel-conflicts}|
367 @emph{Target M680X0 options:}
368 [@b{-l}] [@b{-m68000}|@b{-m68010}|@b{-m68020}|@dots{}]
372 @emph{Target M68HC11 options:}
373 [@b{-m68hc11}|@b{-m68hc12}|@b{-m68hcs12}|@b{-mm9s12x}|@b{-mm9s12xg}]
374 [@b{-mshort}|@b{-mlong}]
375 [@b{-mshort-double}|@b{-mlong-double}]
376 [@b{--force-long-branches}] [@b{--short-branches}]
377 [@b{--strict-direct-mode}] [@b{--print-insn-syntax}]
378 [@b{--print-opcodes}] [@b{--generate-example}]
382 @emph{Target MCORE options:}
383 [@b{-jsri2bsr}] [@b{-sifilter}] [@b{-relax}]
384 [@b{-mcpu=[210|340]}]
388 @emph{Target Meta options:}
389 [@b{-mcpu=@var{cpu}}] [@b{-mfpu=@var{cpu}}] [@b{-mdsp=@var{cpu}}]
392 @emph{Target MICROBLAZE options:}
393 @c MicroBlaze has no machine-dependent assembler options.
397 @emph{Target MIPS options:}
398 [@b{-nocpp}] [@b{-EL}] [@b{-EB}] [@b{-O}[@var{optimization level}]]
399 [@b{-g}[@var{debug level}]] [@b{-G} @var{num}] [@b{-KPIC}] [@b{-call_shared}]
400 [@b{-non_shared}] [@b{-xgot} [@b{-mvxworks-pic}]
401 [@b{-mabi}=@var{ABI}] [@b{-32}] [@b{-n32}] [@b{-64}] [@b{-mfp32}] [@b{-mgp32}]
402 [@b{-march}=@var{CPU}] [@b{-mtune}=@var{CPU}] [@b{-mips1}] [@b{-mips2}]
403 [@b{-mips3}] [@b{-mips4}] [@b{-mips5}] [@b{-mips32}] [@b{-mips32r2}]
404 [@b{-mips64}] [@b{-mips64r2}]
405 [@b{-construct-floats}] [@b{-no-construct-floats}]
406 [@b{-mnan=@var{encoding}}]
407 [@b{-trap}] [@b{-no-break}] [@b{-break}] [@b{-no-trap}]
408 [@b{-mips16}] [@b{-no-mips16}]
409 [@b{-mmicromips}] [@b{-mno-micromips}]
410 [@b{-msmartmips}] [@b{-mno-smartmips}]
411 [@b{-mips3d}] [@b{-no-mips3d}]
412 [@b{-mdmx}] [@b{-no-mdmx}]
413 [@b{-mdsp}] [@b{-mno-dsp}]
414 [@b{-mdspr2}] [@b{-mno-dspr2}]
415 [@b{-mmsa}] [@b{-mno-msa}]
416 [@b{-mmt}] [@b{-mno-mt}]
417 [@b{-mmcu}] [@b{-mno-mcu}]
418 [@b{-minsn32}] [@b{-mno-insn32}]
419 [@b{-mfix7000}] [@b{-mno-fix7000}]
420 [@b{-mfix-rm7000}] [@b{-mno-fix-rm7000}]
421 [@b{-mfix-vr4120}] [@b{-mno-fix-vr4120}]
422 [@b{-mfix-vr4130}] [@b{-mno-fix-vr4130}]
423 [@b{-mdebug}] [@b{-no-mdebug}]
424 [@b{-mpdr}] [@b{-mno-pdr}]
428 @emph{Target MMIX options:}
429 [@b{--fixed-special-register-names}] [@b{--globalize-symbols}]
430 [@b{--gnu-syntax}] [@b{--relax}] [@b{--no-predefined-symbols}]
431 [@b{--no-expand}] [@b{--no-merge-gregs}] [@b{-x}]
432 [@b{--linker-allocated-gregs}]
436 @emph{Target Nios II options:}
437 [@b{-relax-all}] [@b{-relax-section}] [@b{-no-relax}]
442 @emph{Target NDS32 options:}
443 [@b{-EL}] [@b{-EB}] [@b{-O}] [@b{-Os}] [@b{-mcpu=@var{cpu}}]
444 [@b{-misa=@var{isa}}] [@b{-mabi=@var{abi}}] [@b{-mall-ext}]
445 [@b{-m[no-]16-bit}] [@b{-m[no-]perf-ext}] [@b{-m[no-]perf2-ext}]
446 [@b{-m[no-]string-ext}] [@b{-m[no-]dsp-ext}] [@b{-m[no-]mac}] [@b{-m[no-]div}]
447 [@b{-m[no-]audio-isa-ext}] [@b{-m[no-]fpu-sp-ext}] [@b{-m[no-]fpu-dp-ext}]
448 [@b{-m[no-]fpu-fma}] [@b{-mfpu-freg=@var{FREG}}] [@b{-mreduced-regs}]
449 [@b{-mfull-regs}] [@b{-m[no-]dx-regs}] [@b{-mpic}] [@b{-mno-relax}]
454 @emph{Target PDP11 options:}
455 [@b{-mpic}|@b{-mno-pic}] [@b{-mall}] [@b{-mno-extensions}]
456 [@b{-m}@var{extension}|@b{-mno-}@var{extension}]
457 [@b{-m}@var{cpu}] [@b{-m}@var{machine}]
461 @emph{Target picoJava options:}
466 @emph{Target PowerPC options:}
468 [@b{-mpwrx}|@b{-mpwr2}|@b{-mpwr}|@b{-m601}|@b{-mppc}|@b{-mppc32}|@b{-m603}|@b{-m604}|@b{-m403}|@b{-m405}|
469 @b{-m440}|@b{-m464}|@b{-m476}|@b{-m7400}|@b{-m7410}|@b{-m7450}|@b{-m7455}|@b{-m750cl}|@b{-mppc64}|
470 @b{-m620}|@b{-me500}|@b{-e500x2}|@b{-me500mc}|@b{-me500mc64}|@b{-me5500}|@b{-me6500}|@b{-mppc64bridge}|
471 @b{-mbooke}|@b{-mpower4}|@b{-mpwr4}|@b{-mpower5}|@b{-mpwr5}|@b{-mpwr5x}|@b{-mpower6}|@b{-mpwr6}|
472 @b{-mpower7}|@b{-mpwr7}|@b{-mpower8}|@b{-mpwr8}|@b{-ma2}|@b{-mcell}|@b{-mspe}|@b{-mtitan}|@b{-me300}|@b{-mcom}]
473 [@b{-many}] [@b{-maltivec}|@b{-mvsx}|@b{-mhtm}|@b{-mvle}]
474 [@b{-mregnames}|@b{-mno-regnames}]
475 [@b{-mrelocatable}|@b{-mrelocatable-lib}|@b{-K PIC}] [@b{-memb}]
476 [@b{-mlittle}|@b{-mlittle-endian}|@b{-le}|@b{-mbig}|@b{-mbig-endian}|@b{-be}]
477 [@b{-msolaris}|@b{-mno-solaris}]
478 [@b{-nops=@var{count}}]
482 @emph{Target RX options:}
483 [@b{-mlittle-endian}|@b{-mbig-endian}]
484 [@b{-m32bit-doubles}|@b{-m64bit-doubles}]
485 [@b{-muse-conventional-section-names}]
486 [@b{-msmall-data-limit}]
489 [@b{-mint-register=@var{number}}]
490 [@b{-mgcc-abi}|@b{-mrx-abi}]
494 @emph{Target s390 options:}
495 [@b{-m31}|@b{-m64}] [@b{-mesa}|@b{-mzarch}] [@b{-march}=@var{CPU}]
496 [@b{-mregnames}|@b{-mno-regnames}]
497 [@b{-mwarn-areg-zero}]
501 @emph{Target SCORE options:}
502 [@b{-EB}][@b{-EL}][@b{-FIXDD}][@b{-NWARN}]
503 [@b{-SCORE5}][@b{-SCORE5U}][@b{-SCORE7}][@b{-SCORE3}]
504 [@b{-march=score7}][@b{-march=score3}]
505 [@b{-USE_R1}][@b{-KPIC}][@b{-O0}][@b{-G} @var{num}][@b{-V}]
509 @emph{Target SPARC options:}
510 @c The order here is important. See c-sparc.texi.
511 [@b{-Av6}|@b{-Av7}|@b{-Av8}|@b{-Asparclet}|@b{-Asparclite}
512 @b{-Av8plus}|@b{-Av8plusa}|@b{-Av9}|@b{-Av9a}]
513 [@b{-xarch=v8plus}|@b{-xarch=v8plusa}] [@b{-bump}]
518 @emph{Target TIC54X options:}
519 [@b{-mcpu=54[123589]}|@b{-mcpu=54[56]lp}] [@b{-mfar-mode}|@b{-mf}]
520 [@b{-merrors-to-file} @var{<filename>}|@b{-me} @var{<filename>}]
525 @emph{Target TIC6X options:}
526 [@b{-march=@var{arch}}] [@b{-mbig-endian}|@b{-mlittle-endian}]
527 [@b{-mdsbt}|@b{-mno-dsbt}] [@b{-mpid=no}|@b{-mpid=near}|@b{-mpid=far}]
528 [@b{-mpic}|@b{-mno-pic}]
532 @emph{Target TILE-Gx options:}
533 [@b{-m32}|@b{-m64}][@b{-EB}][@b{-EL}]
536 @c TILEPro has no machine-dependent assembler options
541 @emph{Target Xtensa options:}
542 [@b{--[no-]text-section-literals}] [@b{--[no-]absolute-literals}]
543 [@b{--[no-]target-align}] [@b{--[no-]longcalls}]
544 [@b{--[no-]transform}]
545 [@b{--rename-section} @var{oldname}=@var{newname}]
550 @emph{Target Z80 options:}
551 [@b{-z80}] [@b{-r800}]
552 [@b{ -ignore-undocumented-instructions}] [@b{-Wnud}]
553 [@b{ -ignore-unportable-instructions}] [@b{-Wnup}]
554 [@b{ -warn-undocumented-instructions}] [@b{-Wud}]
555 [@b{ -warn-unportable-instructions}] [@b{-Wup}]
556 [@b{ -forbid-undocumented-instructions}] [@b{-Fud}]
557 [@b{ -forbid-unportable-instructions}] [@b{-Fup}]
561 @c Z8000 has no machine-dependent assembler options
570 @include at-file.texi
573 Turn on listings, in any of a variety of ways:
577 omit false conditionals
580 omit debugging directives
583 include general information, like @value{AS} version and options passed
586 include high-level source
592 include macro expansions
595 omit forms processing
601 set the name of the listing file
604 You may combine these options; for example, use @samp{-aln} for assembly
605 listing without forms processing. The @samp{=file} option, if used, must be
606 the last one. By itself, @samp{-a} defaults to @samp{-ahls}.
609 Begin in alternate macro mode.
611 @xref{Altmacro,,@code{.altmacro}}.
614 @item --compress-debug-sections
615 Compress DWARF debug sections using zlib. The debug sections are renamed
616 to begin with @samp{.zdebug}, and the resulting object file may not be
617 compatible with older linkers and object file utilities.
619 @item --nocompress-debug-sections
620 Do not compress DWARF debug sections. This is the default.
623 Ignored. This option is accepted for script compatibility with calls to
626 @item --debug-prefix-map @var{old}=@var{new}
627 When assembling files in directory @file{@var{old}}, record debugging
628 information describing them as in @file{@var{new}} instead.
630 @item --defsym @var{sym}=@var{value}
631 Define the symbol @var{sym} to be @var{value} before assembling the input file.
632 @var{value} must be an integer constant. As in C, a leading @samp{0x}
633 indicates a hexadecimal value, and a leading @samp{0} indicates an octal
634 value. The value of the symbol can be overridden inside a source file via the
635 use of a @code{.set} pseudo-op.
638 ``fast''---skip whitespace and comment preprocessing (assume source is
643 Generate debugging information for each assembler source line using whichever
644 debug format is preferred by the target. This currently means either STABS,
648 Generate stabs debugging information for each assembler line. This
649 may help debugging assembler code, if the debugger can handle it.
652 Generate stabs debugging information for each assembler line, with GNU
653 extensions that probably only gdb can handle, and that could make other
654 debuggers crash or refuse to read your program. This
655 may help debugging assembler code. Currently the only GNU extension is
656 the location of the current working directory at assembling time.
659 Generate DWARF2 debugging information for each assembler line. This
660 may help debugging assembler code, if the debugger can handle it. Note---this
661 option is only supported by some targets, not all of them.
663 @item --gdwarf-sections
664 Instead of creating a .debug_line section, create a series of
665 .debug_line.@var{foo} sections where @var{foo} is the name of the
666 corresponding code section. For example a code section called @var{.text.func}
667 will have its dwarf line number information placed into a section called
668 @var{.debug_line.text.func}. If the code section is just called @var{.text}
669 then debug line section will still be called just @var{.debug_line} without any
672 @item --size-check=error
673 @itemx --size-check=warning
674 Issue an error or warning for invalid ELF .size directive.
677 Print a summary of the command line options and exit.
680 Print a summary of all target specific options and exit.
683 Add directory @var{dir} to the search list for @code{.include} directives.
686 Don't warn about signed overflow.
689 @ifclear DIFF-TBL-KLUGE
690 This option is accepted but has no effect on the @value{TARGET} family.
692 @ifset DIFF-TBL-KLUGE
693 Issue warnings when difference tables altered for long displacements.
698 Keep (in the symbol table) local symbols. These symbols start with
699 system-specific local label prefixes, typically @samp{.L} for ELF systems
700 or @samp{L} for traditional a.out systems.
705 @item --listing-lhs-width=@var{number}
706 Set the maximum width, in words, of the output data column for an assembler
707 listing to @var{number}.
709 @item --listing-lhs-width2=@var{number}
710 Set the maximum width, in words, of the output data column for continuation
711 lines in an assembler listing to @var{number}.
713 @item --listing-rhs-width=@var{number}
714 Set the maximum width of an input source line, as displayed in a listing, to
717 @item --listing-cont-lines=@var{number}
718 Set the maximum number of lines printed in a listing for a single line of input
721 @item -o @var{objfile}
722 Name the object-file output from @command{@value{AS}} @var{objfile}.
725 Fold the data section into the text section.
727 @kindex --hash-size=@var{number}
728 Set the default size of GAS's hash tables to a prime number close to
729 @var{number}. Increasing this value can reduce the length of time it takes the
730 assembler to perform its tasks, at the expense of increasing the assembler's
731 memory requirements. Similarly reducing this value can reduce the memory
732 requirements at the expense of speed.
734 @item --reduce-memory-overheads
735 This option reduces GAS's memory requirements, at the expense of making the
736 assembly processes slower. Currently this switch is a synonym for
737 @samp{--hash-size=4051}, but in the future it may have other effects as well.
740 Print the maximum space (in bytes) and total time (in seconds) used by
743 @item --strip-local-absolute
744 Remove local absolute symbols from the outgoing symbol table.
748 Print the @command{as} version.
751 Print the @command{as} version and exit.
755 Suppress warning messages.
757 @item --fatal-warnings
758 Treat warnings as errors.
761 Don't suppress warning messages or treat them as errors.
770 Generate an object file even after errors.
772 @item -- | @var{files} @dots{}
773 Standard input, or source files to assemble.
781 @xref{AArch64 Options}, for the options available when @value{AS} is configured
782 for the 64-bit mode of the ARM Architecture (AArch64).
787 The following options are available when @value{AS} is configured for the
788 64-bit mode of the ARM Architecture (AArch64).
791 @include c-aarch64.texi
792 @c ended inside the included file
800 @xref{Alpha Options}, for the options available when @value{AS} is configured
801 for an Alpha processor.
806 The following options are available when @value{AS} is configured for an Alpha
810 @include c-alpha.texi
811 @c ended inside the included file
818 The following options are available when @value{AS} is configured for
823 This option selects the core processor variant.
825 Select either big-endian (-EB) or little-endian (-EL) output.
830 The following options are available when @value{AS} is configured for the ARM
834 @item -mcpu=@var{processor}[+@var{extension}@dots{}]
835 Specify which ARM processor variant is the target.
836 @item -march=@var{architecture}[+@var{extension}@dots{}]
837 Specify which ARM architecture variant is used by the target.
838 @item -mfpu=@var{floating-point-format}
839 Select which Floating Point architecture is the target.
840 @item -mfloat-abi=@var{abi}
841 Select which floating point ABI is in use.
843 Enable Thumb only instruction decoding.
844 @item -mapcs-32 | -mapcs-26 | -mapcs-float | -mapcs-reentrant
845 Select which procedure calling convention is in use.
847 Select either big-endian (-EB) or little-endian (-EL) output.
848 @item -mthumb-interwork
849 Specify that the code has been generated with interworking between Thumb and
852 Turns on CodeComposer Studio assembly syntax compatibility mode.
854 Specify that PIC code has been generated.
862 @xref{Blackfin Options}, for the options available when @value{AS} is
863 configured for the Blackfin processor family.
868 The following options are available when @value{AS} is configured for
869 the Blackfin processor family.
873 @c ended inside the included file
880 See the info pages for documentation of the CRIS-specific options.
884 The following options are available when @value{AS} is configured for
887 @cindex D10V optimization
888 @cindex optimization, D10V
890 Optimize output by parallelizing instructions.
895 The following options are available when @value{AS} is configured for a D30V
898 @cindex D30V optimization
899 @cindex optimization, D30V
901 Optimize output by parallelizing instructions.
905 Warn when nops are generated.
907 @cindex D30V nops after 32-bit multiply
909 Warn when a nop after a 32-bit multiply instruction is generated.
915 The following options are available when @value{AS} is configured for the
916 Adapteva EPIPHANY series.
919 @xref{Epiphany Options}, for the options available when @value{AS} is
920 configured for an Epiphany processor.
925 The following options are available when @value{AS} is configured for
926 an Epiphany processor.
929 @include c-epiphany.texi
930 @c ended inside the included file
938 @xref{H8/300 Options}, for the options available when @value{AS} is configured
939 for an H8/300 processor.
944 The following options are available when @value{AS} is configured for an H8/300
948 @include c-h8300.texi
949 @c ended inside the included file
957 @xref{i386-Options}, for the options available when @value{AS} is
958 configured for an i386 processor.
963 The following options are available when @value{AS} is configured for
968 @c ended inside the included file
975 The following options are available when @value{AS} is configured for the
976 Intel 80960 processor.
979 @item -ACA | -ACA_A | -ACB | -ACC | -AKA | -AKB | -AKC | -AMC
980 Specify which variant of the 960 architecture is the target.
983 Add code to collect statistics about branches taken.
986 Do not alter compare-and-branch instructions for long displacements;
993 The following options are available when @value{AS} is configured for the
999 Specifies that the extended IP2022 instructions are allowed.
1002 Restores the default behaviour, which restricts the permitted instructions to
1003 just the basic IP2022 ones.
1009 The following options are available when @value{AS} is configured for the
1010 Renesas M32C and M16C processors.
1015 Assemble M32C instructions.
1018 Assemble M16C instructions (the default).
1021 Enable support for link-time relaxations.
1024 Support H'00 style hex constants in addition to 0x00 style.
1030 The following options are available when @value{AS} is configured for the
1031 Renesas M32R (formerly Mitsubishi M32R) series.
1036 Specify which processor in the M32R family is the target. The default
1037 is normally the M32R, but this option changes it to the M32RX.
1039 @item --warn-explicit-parallel-conflicts or --Wp
1040 Produce warning messages when questionable parallel constructs are
1043 @item --no-warn-explicit-parallel-conflicts or --Wnp
1044 Do not produce warning messages when questionable parallel constructs are
1051 The following options are available when @value{AS} is configured for the
1052 Motorola 68000 series.
1057 Shorten references to undefined symbols, to one word instead of two.
1059 @item -m68000 | -m68008 | -m68010 | -m68020 | -m68030
1060 @itemx | -m68040 | -m68060 | -m68302 | -m68331 | -m68332
1061 @itemx | -m68333 | -m68340 | -mcpu32 | -m5200
1062 Specify what processor in the 68000 family is the target. The default
1063 is normally the 68020, but this can be changed at configuration time.
1065 @item -m68881 | -m68882 | -mno-68881 | -mno-68882
1066 The target machine does (or does not) have a floating-point coprocessor.
1067 The default is to assume a coprocessor for 68020, 68030, and cpu32. Although
1068 the basic 68000 is not compatible with the 68881, a combination of the
1069 two can be specified, since it's possible to do emulation of the
1070 coprocessor instructions with the main processor.
1072 @item -m68851 | -mno-68851
1073 The target machine does (or does not) have a memory-management
1074 unit coprocessor. The default is to assume an MMU for 68020 and up.
1082 @xref{Nios II Options}, for the options available when @value{AS} is configured
1083 for an Altera Nios II processor.
1087 @c man begin OPTIONS
1088 The following options are available when @value{AS} is configured for an
1089 Altera Nios II processor.
1091 @c man begin INCLUDE
1092 @include c-nios2.texi
1093 @c ended inside the included file
1099 For details about the PDP-11 machine dependent features options,
1100 see @ref{PDP-11-Options}.
1103 @item -mpic | -mno-pic
1104 Generate position-independent (or position-dependent) code. The
1105 default is @option{-mpic}.
1108 @itemx -mall-extensions
1109 Enable all instruction set extensions. This is the default.
1111 @item -mno-extensions
1112 Disable all instruction set extensions.
1114 @item -m@var{extension} | -mno-@var{extension}
1115 Enable (or disable) a particular instruction set extension.
1118 Enable the instruction set extensions supported by a particular CPU, and
1119 disable all other extensions.
1121 @item -m@var{machine}
1122 Enable the instruction set extensions supported by a particular machine
1123 model, and disable all other extensions.
1129 The following options are available when @value{AS} is configured for
1130 a picoJava processor.
1134 @cindex PJ endianness
1135 @cindex endianness, PJ
1136 @cindex big endian output, PJ
1138 Generate ``big endian'' format output.
1140 @cindex little endian output, PJ
1142 Generate ``little endian'' format output.
1148 The following options are available when @value{AS} is configured for the
1149 Motorola 68HC11 or 68HC12 series.
1153 @item -m68hc11 | -m68hc12 | -m68hcs12 | -mm9s12x | -mm9s12xg
1154 Specify what processor is the target. The default is
1155 defined by the configuration option when building the assembler.
1157 @item --xgate-ramoffset
1158 Instruct the linker to offset RAM addresses from S12X address space into
1159 XGATE address space.
1162 Specify to use the 16-bit integer ABI.
1165 Specify to use the 32-bit integer ABI.
1167 @item -mshort-double
1168 Specify to use the 32-bit double ABI.
1171 Specify to use the 64-bit double ABI.
1173 @item --force-long-branches
1174 Relative branches are turned into absolute ones. This concerns
1175 conditional branches, unconditional branches and branches to a
1178 @item -S | --short-branches
1179 Do not turn relative branches into absolute ones
1180 when the offset is out of range.
1182 @item --strict-direct-mode
1183 Do not turn the direct addressing mode into extended addressing mode
1184 when the instruction does not support direct addressing mode.
1186 @item --print-insn-syntax
1187 Print the syntax of instruction in case of error.
1189 @item --print-opcodes
1190 Print the list of instructions with syntax and then exit.
1192 @item --generate-example
1193 Print an example of instruction for each possible instruction and then exit.
1194 This option is only useful for testing @command{@value{AS}}.
1200 The following options are available when @command{@value{AS}} is configured
1201 for the SPARC architecture:
1204 @item -Av6 | -Av7 | -Av8 | -Asparclet | -Asparclite
1205 @itemx -Av8plus | -Av8plusa | -Av9 | -Av9a
1206 Explicitly select a variant of the SPARC architecture.
1208 @samp{-Av8plus} and @samp{-Av8plusa} select a 32 bit environment.
1209 @samp{-Av9} and @samp{-Av9a} select a 64 bit environment.
1211 @samp{-Av8plusa} and @samp{-Av9a} enable the SPARC V9 instruction set with
1212 UltraSPARC extensions.
1214 @item -xarch=v8plus | -xarch=v8plusa
1215 For compatibility with the Solaris v9 assembler. These options are
1216 equivalent to -Av8plus and -Av8plusa, respectively.
1219 Warn when the assembler switches to another architecture.
1224 The following options are available when @value{AS} is configured for the 'c54x
1229 Enable extended addressing mode. All addresses and relocations will assume
1230 extended addressing (usually 23 bits).
1231 @item -mcpu=@var{CPU_VERSION}
1232 Sets the CPU version being compiled for.
1233 @item -merrors-to-file @var{FILENAME}
1234 Redirect error output to a file, for broken systems which don't support such
1235 behaviour in the shell.
1240 The following options are available when @value{AS} is configured for
1245 This option sets the largest size of an object that can be referenced
1246 implicitly with the @code{gp} register. It is only accepted for targets that
1247 use ECOFF format, such as a DECstation running Ultrix. The default value is 8.
1249 @cindex MIPS endianness
1250 @cindex endianness, MIPS
1251 @cindex big endian output, MIPS
1253 Generate ``big endian'' format output.
1255 @cindex little endian output, MIPS
1257 Generate ``little endian'' format output.
1269 Generate code for a particular MIPS Instruction Set Architecture level.
1270 @samp{-mips1} is an alias for @samp{-march=r3000}, @samp{-mips2} is an
1271 alias for @samp{-march=r6000}, @samp{-mips3} is an alias for
1272 @samp{-march=r4000} and @samp{-mips4} is an alias for @samp{-march=r8000}.
1273 @samp{-mips5}, @samp{-mips32}, @samp{-mips32r2}, @samp{-mips64}, and
1274 @samp{-mips64r2} correspond to generic MIPS V, MIPS32, MIPS32 Release 2,
1275 MIPS64, and MIPS64 Release 2 ISA processors, respectively.
1277 @item -march=@var{cpu}
1278 Generate code for a particular MIPS CPU.
1280 @item -mtune=@var{cpu}
1281 Schedule and tune for a particular MIPS CPU.
1285 Cause nops to be inserted if the read of the destination register
1286 of an mfhi or mflo instruction occurs in the following two instructions.
1289 @itemx -mno-fix-rm7000
1290 Cause nops to be inserted if a dmult or dmultu instruction is
1291 followed by a load instruction.
1295 Cause stabs-style debugging output to go into an ECOFF-style .mdebug
1296 section instead of the standard ELF .stabs sections.
1300 Control generation of @code{.pdr} sections.
1304 The register sizes are normally inferred from the ISA and ABI, but these
1305 flags force a certain group of registers to be treated as 32 bits wide at
1306 all times. @samp{-mgp32} controls the size of general-purpose registers
1307 and @samp{-mfp32} controls the size of floating-point registers.
1311 Generate code for the MIPS 16 processor. This is equivalent to putting
1312 @code{.set mips16} at the start of the assembly file. @samp{-no-mips16}
1313 turns off this option.
1316 @itemx -mno-micromips
1317 Generate code for the microMIPS processor. This is equivalent to putting
1318 @code{.set micromips} at the start of the assembly file. @samp{-mno-micromips}
1319 turns off this option. This is equivalent to putting @code{.set nomicromips}
1320 at the start of the assembly file.
1323 @itemx -mno-smartmips
1324 Enables the SmartMIPS extension to the MIPS32 instruction set. This is
1325 equivalent to putting @code{.set smartmips} at the start of the assembly file.
1326 @samp{-mno-smartmips} turns off this option.
1330 Generate code for the MIPS-3D Application Specific Extension.
1331 This tells the assembler to accept MIPS-3D instructions.
1332 @samp{-no-mips3d} turns off this option.
1336 Generate code for the MDMX Application Specific Extension.
1337 This tells the assembler to accept MDMX instructions.
1338 @samp{-no-mdmx} turns off this option.
1342 Generate code for the DSP Release 1 Application Specific Extension.
1343 This tells the assembler to accept DSP Release 1 instructions.
1344 @samp{-mno-dsp} turns off this option.
1348 Generate code for the DSP Release 2 Application Specific Extension.
1349 This option implies -mdsp.
1350 This tells the assembler to accept DSP Release 2 instructions.
1351 @samp{-mno-dspr2} turns off this option.
1355 Generate code for the MIPS SIMD Architecture Extension.
1356 This tells the assembler to accept MSA instructions.
1357 @samp{-mno-msa} turns off this option.
1361 Generate code for the MT Application Specific Extension.
1362 This tells the assembler to accept MT instructions.
1363 @samp{-mno-mt} turns off this option.
1367 Generate code for the MCU Application Specific Extension.
1368 This tells the assembler to accept MCU instructions.
1369 @samp{-mno-mcu} turns off this option.
1373 Only use 32-bit instruction encodings when generating code for the
1374 microMIPS processor. This option inhibits the use of any 16-bit
1375 instructions. This is equivalent to putting @code{.set insn32} at
1376 the start of the assembly file. @samp{-mno-insn32} turns off this
1377 option. This is equivalent to putting @code{.set noinsn32} at the
1378 start of the assembly file. By default @samp{-mno-insn32} is
1379 selected, allowing all instructions to be used.
1381 @item --construct-floats
1382 @itemx --no-construct-floats
1383 The @samp{--no-construct-floats} option disables the construction of
1384 double width floating point constants by loading the two halves of the
1385 value into the two single width floating point registers that make up
1386 the double width register. By default @samp{--construct-floats} is
1387 selected, allowing construction of these floating point constants.
1389 @item --relax-branch
1390 @itemx --no-relax-branch
1391 The @samp{--relax-branch} option enables the relaxation of out-of-range
1392 branches. By default @samp{--no-relax-branch} is selected, causing any
1393 out-of-range branches to produce an error.
1395 @item -mnan=@var{encoding}
1396 Select between the IEEE 754-2008 (@option{-mnan=2008}) or the legacy
1397 (@option{-mnan=legacy}) NaN encoding format. The latter is the default.
1400 @item --emulation=@var{name}
1401 This option was formerly used to switch between ELF and ECOFF output
1402 on targets like IRIX 5 that supported both. MIPS ECOFF support was
1403 removed in GAS 2.24, so the option now serves little purpose.
1404 It is retained for backwards compatibility.
1406 The available configuration names are: @samp{mipself}, @samp{mipslelf} and
1407 @samp{mipsbelf}. Choosing @samp{mipself} now has no effect, since the output
1408 is always ELF. @samp{mipslelf} and @samp{mipsbelf} select little- and
1409 big-endian output respectively, but @samp{-EL} and @samp{-EB} are now the
1410 preferred options instead.
1413 @command{@value{AS}} ignores this option. It is accepted for compatibility with
1420 Control how to deal with multiplication overflow and division by zero.
1421 @samp{--trap} or @samp{--no-break} (which are synonyms) take a trap exception
1422 (and only work for Instruction Set Architecture level 2 and higher);
1423 @samp{--break} or @samp{--no-trap} (also synonyms, and the default) take a
1427 When this option is used, @command{@value{AS}} will issue a warning every
1428 time it generates a nop instruction from a macro.
1433 The following options are available when @value{AS} is configured for
1439 Enable or disable the JSRI to BSR transformation. By default this is enabled.
1440 The command line option @samp{-nojsri2bsr} can be used to disable it.
1444 Enable or disable the silicon filter behaviour. By default this is disabled.
1445 The default can be overridden by the @samp{-sifilter} command line option.
1448 Alter jump instructions for long displacements.
1450 @item -mcpu=[210|340]
1451 Select the cpu type on the target hardware. This controls which instructions
1455 Assemble for a big endian target.
1458 Assemble for a little endian target.
1467 @xref{Meta Options}, for the options available when @value{AS} is configured
1468 for a Meta processor.
1472 @c man begin OPTIONS
1473 The following options are available when @value{AS} is configured for a
1476 @c man begin INCLUDE
1477 @include c-metag.texi
1478 @c ended inside the included file
1483 @c man begin OPTIONS
1485 See the info pages for documentation of the MMIX-specific options.
1491 @xref{NDS32 Options}, for the options available when @value{AS} is configured
1492 for a NDS32 processor.
1494 @c ended inside the included file
1498 @c man begin OPTIONS
1499 The following options are available when @value{AS} is configured for a
1502 @c man begin INCLUDE
1503 @include c-nds32.texi
1504 @c ended inside the included file
1511 @xref{PowerPC-Opts}, for the options available when @value{AS} is configured
1512 for a PowerPC processor.
1516 @c man begin OPTIONS
1517 The following options are available when @value{AS} is configured for a
1520 @c man begin INCLUDE
1522 @c ended inside the included file
1527 @c man begin OPTIONS
1529 See the info pages for documentation of the RX-specific options.
1533 The following options are available when @value{AS} is configured for the s390
1539 Select the word size, either 31/32 bits or 64 bits.
1542 Select the architecture mode, either the Enterprise System
1543 Architecture (esa) or the z/Architecture mode (zarch).
1544 @item -march=@var{processor}
1545 Specify which s390 processor variant is the target, @samp{g6}, @samp{g6},
1546 @samp{z900}, @samp{z990}, @samp{z9-109}, @samp{z9-ec}, @samp{z10},
1547 @samp{z196}, or @samp{zEC12}.
1549 @itemx -mno-regnames
1550 Allow or disallow symbolic names for registers.
1551 @item -mwarn-areg-zero
1552 Warn whenever the operand for a base or index register has been specified
1553 but evaluates to zero.
1561 @xref{TIC6X Options}, for the options available when @value{AS} is configured
1562 for a TMS320C6000 processor.
1566 @c man begin OPTIONS
1567 The following options are available when @value{AS} is configured for a
1568 TMS320C6000 processor.
1570 @c man begin INCLUDE
1571 @include c-tic6x.texi
1572 @c ended inside the included file
1580 @xref{TILE-Gx Options}, for the options available when @value{AS} is configured
1581 for a TILE-Gx processor.
1585 @c man begin OPTIONS
1586 The following options are available when @value{AS} is configured for a TILE-Gx
1589 @c man begin INCLUDE
1590 @include c-tilegx.texi
1591 @c ended inside the included file
1599 @xref{Xtensa Options}, for the options available when @value{AS} is configured
1600 for an Xtensa processor.
1604 @c man begin OPTIONS
1605 The following options are available when @value{AS} is configured for an
1608 @c man begin INCLUDE
1609 @include c-xtensa.texi
1610 @c ended inside the included file
1615 @c man begin OPTIONS
1618 The following options are available when @value{AS} is configured for
1619 a Z80 family processor.
1622 Assemble for Z80 processor.
1624 Assemble for R800 processor.
1625 @item -ignore-undocumented-instructions
1627 Assemble undocumented Z80 instructions that also work on R800 without warning.
1628 @item -ignore-unportable-instructions
1630 Assemble all undocumented Z80 instructions without warning.
1631 @item -warn-undocumented-instructions
1633 Issue a warning for undocumented Z80 instructions that also work on R800.
1634 @item -warn-unportable-instructions
1636 Issue a warning for undocumented Z80 instructions that do not work on R800.
1637 @item -forbid-undocumented-instructions
1639 Treat all undocumented instructions as errors.
1640 @item -forbid-unportable-instructions
1642 Treat undocumented Z80 instructions that do not work on R800 as errors.
1649 * Manual:: Structure of this Manual
1650 * GNU Assembler:: The GNU Assembler
1651 * Object Formats:: Object File Formats
1652 * Command Line:: Command Line
1653 * Input Files:: Input Files
1654 * Object:: Output (Object) File
1655 * Errors:: Error and Warning Messages
1659 @section Structure of this Manual
1661 @cindex manual, structure and purpose
1662 This manual is intended to describe what you need to know to use
1663 @sc{gnu} @command{@value{AS}}. We cover the syntax expected in source files, including
1664 notation for symbols, constants, and expressions; the directives that
1665 @command{@value{AS}} understands; and of course how to invoke @command{@value{AS}}.
1668 We also cover special features in the @value{TARGET}
1669 configuration of @command{@value{AS}}, including assembler directives.
1672 This manual also describes some of the machine-dependent features of
1673 various flavors of the assembler.
1676 @cindex machine instructions (not covered)
1677 On the other hand, this manual is @emph{not} intended as an introduction
1678 to programming in assembly language---let alone programming in general!
1679 In a similar vein, we make no attempt to introduce the machine
1680 architecture; we do @emph{not} describe the instruction set, standard
1681 mnemonics, registers or addressing modes that are standard to a
1682 particular architecture.
1684 You may want to consult the manufacturer's
1685 machine architecture manual for this information.
1689 For information on the H8/300 machine instruction set, see @cite{H8/300
1690 Series Programming Manual}. For the H8/300H, see @cite{H8/300H Series
1691 Programming Manual} (Renesas).
1694 For information on the Renesas (formerly Hitachi) / SuperH SH machine instruction set,
1695 see @cite{SH-Microcomputer User's Manual} (Renesas) or
1696 @cite{SH-4 32-bit CPU Core Architecture} (SuperH) and
1697 @cite{SuperH (SH) 64-Bit RISC Series} (SuperH).
1700 For information on the Z8000 machine instruction set, see @cite{Z8000 CPU Technical Manual}
1704 @c I think this is premature---doc@cygnus.com, 17jan1991
1706 Throughout this manual, we assume that you are running @dfn{GNU},
1707 the portable operating system from the @dfn{Free Software
1708 Foundation, Inc.}. This restricts our attention to certain kinds of
1709 computer (in particular, the kinds of computers that @sc{gnu} can run on);
1710 once this assumption is granted examples and definitions need less
1713 @command{@value{AS}} is part of a team of programs that turn a high-level
1714 human-readable series of instructions into a low-level
1715 computer-readable series of instructions. Different versions of
1716 @command{@value{AS}} are used for different kinds of computer.
1719 @c There used to be a section "Terminology" here, which defined
1720 @c "contents", "byte", "word", and "long". Defining "word" to any
1721 @c particular size is confusing when the .word directive may generate 16
1722 @c bits on one machine and 32 bits on another; in general, for the user
1723 @c version of this manual, none of these terms seem essential to define.
1724 @c They were used very little even in the former draft of the manual;
1725 @c this draft makes an effort to avoid them (except in names of
1729 @section The GNU Assembler
1731 @c man begin DESCRIPTION
1733 @sc{gnu} @command{as} is really a family of assemblers.
1735 This manual describes @command{@value{AS}}, a member of that family which is
1736 configured for the @value{TARGET} architectures.
1738 If you use (or have used) the @sc{gnu} assembler on one architecture, you
1739 should find a fairly similar environment when you use it on another
1740 architecture. Each version has much in common with the others,
1741 including object file formats, most assembler directives (often called
1742 @dfn{pseudo-ops}) and assembler syntax.@refill
1744 @cindex purpose of @sc{gnu} assembler
1745 @command{@value{AS}} is primarily intended to assemble the output of the
1746 @sc{gnu} C compiler @code{@value{GCC}} for use by the linker
1747 @code{@value{LD}}. Nevertheless, we've tried to make @command{@value{AS}}
1748 assemble correctly everything that other assemblers for the same
1749 machine would assemble.
1751 Any exceptions are documented explicitly (@pxref{Machine Dependencies}).
1754 @c This remark should appear in generic version of manual; assumption
1755 @c here is that generic version sets M680x0.
1756 This doesn't mean @command{@value{AS}} always uses the same syntax as another
1757 assembler for the same architecture; for example, we know of several
1758 incompatible versions of 680x0 assembly language syntax.
1763 Unlike older assemblers, @command{@value{AS}} is designed to assemble a source
1764 program in one pass of the source file. This has a subtle impact on the
1765 @kbd{.org} directive (@pxref{Org,,@code{.org}}).
1767 @node Object Formats
1768 @section Object File Formats
1770 @cindex object file format
1771 The @sc{gnu} assembler can be configured to produce several alternative
1772 object file formats. For the most part, this does not affect how you
1773 write assembly language programs; but directives for debugging symbols
1774 are typically different in different file formats. @xref{Symbol
1775 Attributes,,Symbol Attributes}.
1778 For the @value{TARGET} target, @command{@value{AS}} is configured to produce
1779 @value{OBJ-NAME} format object files.
1781 @c The following should exhaust all configs that set MULTI-OBJ, ideally
1783 On the @value{TARGET}, @command{@value{AS}} can be configured to produce either
1784 @code{b.out} or COFF format object files.
1787 On the @value{TARGET}, @command{@value{AS}} can be configured to produce either
1788 SOM or ELF format object files.
1793 @section Command Line
1795 @cindex command line conventions
1797 After the program name @command{@value{AS}}, the command line may contain
1798 options and file names. Options may appear in any order, and may be
1799 before, after, or between file names. The order of file names is
1802 @cindex standard input, as input file
1804 @file{--} (two hyphens) by itself names the standard input file
1805 explicitly, as one of the files for @command{@value{AS}} to assemble.
1807 @cindex options, command line
1808 Except for @samp{--} any command line argument that begins with a
1809 hyphen (@samp{-}) is an option. Each option changes the behavior of
1810 @command{@value{AS}}. No option changes the way another option works. An
1811 option is a @samp{-} followed by one or more letters; the case of
1812 the letter is important. All options are optional.
1814 Some options expect exactly one file name to follow them. The file
1815 name may either immediately follow the option's letter (compatible
1816 with older assemblers) or it may be the next command argument (@sc{gnu}
1817 standard). These two command lines are equivalent:
1820 @value{AS} -o my-object-file.o mumble.s
1821 @value{AS} -omy-object-file.o mumble.s
1825 @section Input Files
1828 @cindex source program
1829 @cindex files, input
1830 We use the phrase @dfn{source program}, abbreviated @dfn{source}, to
1831 describe the program input to one run of @command{@value{AS}}. The program may
1832 be in one or more files; how the source is partitioned into files
1833 doesn't change the meaning of the source.
1835 @c I added "con" prefix to "catenation" just to prove I can overcome my
1836 @c APL training... doc@cygnus.com
1837 The source program is a concatenation of the text in all the files, in the
1840 @c man begin DESCRIPTION
1841 Each time you run @command{@value{AS}} it assembles exactly one source
1842 program. The source program is made up of one or more files.
1843 (The standard input is also a file.)
1845 You give @command{@value{AS}} a command line that has zero or more input file
1846 names. The input files are read (from left file name to right). A
1847 command line argument (in any position) that has no special meaning
1848 is taken to be an input file name.
1850 If you give @command{@value{AS}} no file names it attempts to read one input file
1851 from the @command{@value{AS}} standard input, which is normally your terminal. You
1852 may have to type @key{ctl-D} to tell @command{@value{AS}} there is no more program
1855 Use @samp{--} if you need to explicitly name the standard input file
1856 in your command line.
1858 If the source is empty, @command{@value{AS}} produces a small, empty object
1863 @subheading Filenames and Line-numbers
1865 @cindex input file linenumbers
1866 @cindex line numbers, in input files
1867 There are two ways of locating a line in the input file (or files) and
1868 either may be used in reporting error messages. One way refers to a line
1869 number in a physical file; the other refers to a line number in a
1870 ``logical'' file. @xref{Errors, ,Error and Warning Messages}.
1872 @dfn{Physical files} are those files named in the command line given
1873 to @command{@value{AS}}.
1875 @dfn{Logical files} are simply names declared explicitly by assembler
1876 directives; they bear no relation to physical files. Logical file names help
1877 error messages reflect the original source file, when @command{@value{AS}} source
1878 is itself synthesized from other files. @command{@value{AS}} understands the
1879 @samp{#} directives emitted by the @code{@value{GCC}} preprocessor. See also
1880 @ref{File,,@code{.file}}.
1883 @section Output (Object) File
1889 Every time you run @command{@value{AS}} it produces an output file, which is
1890 your assembly language program translated into numbers. This file
1891 is the object file. Its default name is
1899 @code{b.out} when @command{@value{AS}} is configured for the Intel 80960.
1901 You can give it another name by using the @option{-o} option. Conventionally,
1902 object file names end with @file{.o}. The default name is used for historical
1903 reasons: older assemblers were capable of assembling self-contained programs
1904 directly into a runnable program. (For some formats, this isn't currently
1905 possible, but it can be done for the @code{a.out} format.)
1909 The object file is meant for input to the linker @code{@value{LD}}. It contains
1910 assembled program code, information to help @code{@value{LD}} integrate
1911 the assembled program into a runnable file, and (optionally) symbolic
1912 information for the debugger.
1914 @c link above to some info file(s) like the description of a.out.
1915 @c don't forget to describe @sc{gnu} info as well as Unix lossage.
1918 @section Error and Warning Messages
1920 @c man begin DESCRIPTION
1922 @cindex error messages
1923 @cindex warning messages
1924 @cindex messages from assembler
1925 @command{@value{AS}} may write warnings and error messages to the standard error
1926 file (usually your terminal). This should not happen when a compiler
1927 runs @command{@value{AS}} automatically. Warnings report an assumption made so
1928 that @command{@value{AS}} could keep assembling a flawed program; errors report a
1929 grave problem that stops the assembly.
1933 @cindex format of warning messages
1934 Warning messages have the format
1937 file_name:@b{NNN}:Warning Message Text
1941 @cindex line numbers, in warnings/errors
1942 (where @b{NNN} is a line number). If a logical file name has been given
1943 (@pxref{File,,@code{.file}}) it is used for the filename, otherwise the name of
1944 the current input file is used. If a logical line number was given
1946 (@pxref{Line,,@code{.line}})
1948 then it is used to calculate the number printed,
1949 otherwise the actual line in the current source file is printed. The
1950 message text is intended to be self explanatory (in the grand Unix
1953 @cindex format of error messages
1954 Error messages have the format
1956 file_name:@b{NNN}:FATAL:Error Message Text
1958 The file name and line number are derived as for warning
1959 messages. The actual message text may be rather less explanatory
1960 because many of them aren't supposed to happen.
1963 @chapter Command-Line Options
1965 @cindex options, all versions of assembler
1966 This chapter describes command-line options available in @emph{all}
1967 versions of the @sc{gnu} assembler; see @ref{Machine Dependencies},
1968 for options specific
1970 to the @value{TARGET} target.
1973 to particular machine architectures.
1976 @c man begin DESCRIPTION
1978 If you are invoking @command{@value{AS}} via the @sc{gnu} C compiler,
1979 you can use the @samp{-Wa} option to pass arguments through to the assembler.
1980 The assembler arguments must be separated from each other (and the @samp{-Wa})
1981 by commas. For example:
1984 gcc -c -g -O -Wa,-alh,-L file.c
1988 This passes two options to the assembler: @samp{-alh} (emit a listing to
1989 standard output with high-level and assembly source) and @samp{-L} (retain
1990 local symbols in the symbol table).
1992 Usually you do not need to use this @samp{-Wa} mechanism, since many compiler
1993 command-line options are automatically passed to the assembler by the compiler.
1994 (You can call the @sc{gnu} compiler driver with the @samp{-v} option to see
1995 precisely what options it passes to each compilation pass, including the
2001 * a:: -a[cdghlns] enable listings
2002 * alternate:: --alternate enable alternate macro syntax
2003 * D:: -D for compatibility
2004 * f:: -f to work faster
2005 * I:: -I for .include search path
2006 @ifclear DIFF-TBL-KLUGE
2007 * K:: -K for compatibility
2009 @ifset DIFF-TBL-KLUGE
2010 * K:: -K for difference tables
2013 * L:: -L to retain local symbols
2014 * listing:: --listing-XXX to configure listing output
2015 * M:: -M or --mri to assemble in MRI compatibility mode
2016 * MD:: --MD for dependency tracking
2017 * o:: -o to name the object file
2018 * R:: -R to join data and text sections
2019 * statistics:: --statistics to see statistics about assembly
2020 * traditional-format:: --traditional-format for compatible output
2021 * v:: -v to announce version
2022 * W:: -W, --no-warn, --warn, --fatal-warnings to control warnings
2023 * Z:: -Z to make object file even after errors
2027 @section Enable Listings: @option{-a[cdghlns]}
2037 @cindex listings, enabling
2038 @cindex assembly listings, enabling
2040 These options enable listing output from the assembler. By itself,
2041 @samp{-a} requests high-level, assembly, and symbols listing.
2042 You can use other letters to select specific options for the list:
2043 @samp{-ah} requests a high-level language listing,
2044 @samp{-al} requests an output-program assembly listing, and
2045 @samp{-as} requests a symbol table listing.
2046 High-level listings require that a compiler debugging option like
2047 @samp{-g} be used, and that assembly listings (@samp{-al}) be requested
2050 Use the @samp{-ag} option to print a first section with general assembly
2051 information, like @value{AS} version, switches passed, or time stamp.
2053 Use the @samp{-ac} option to omit false conditionals from a listing. Any lines
2054 which are not assembled because of a false @code{.if} (or @code{.ifdef}, or any
2055 other conditional), or a true @code{.if} followed by an @code{.else}, will be
2056 omitted from the listing.
2058 Use the @samp{-ad} option to omit debugging directives from the
2061 Once you have specified one of these options, you can further control
2062 listing output and its appearance using the directives @code{.list},
2063 @code{.nolist}, @code{.psize}, @code{.eject}, @code{.title}, and
2065 The @samp{-an} option turns off all forms processing.
2066 If you do not request listing output with one of the @samp{-a} options, the
2067 listing-control directives have no effect.
2069 The letters after @samp{-a} may be combined into one option,
2070 @emph{e.g.}, @samp{-aln}.
2072 Note if the assembler source is coming from the standard input (e.g.,
2074 is being created by @code{@value{GCC}} and the @samp{-pipe} command line switch
2075 is being used) then the listing will not contain any comments or preprocessor
2076 directives. This is because the listing code buffers input source lines from
2077 stdin only after they have been preprocessed by the assembler. This reduces
2078 memory usage and makes the code more efficient.
2081 @section @option{--alternate}
2084 Begin in alternate macro mode, see @ref{Altmacro,,@code{.altmacro}}.
2087 @section @option{-D}
2090 This option has no effect whatsoever, but it is accepted to make it more
2091 likely that scripts written for other assemblers also work with
2092 @command{@value{AS}}.
2095 @section Work Faster: @option{-f}
2098 @cindex trusted compiler
2099 @cindex faster processing (@option{-f})
2100 @samp{-f} should only be used when assembling programs written by a
2101 (trusted) compiler. @samp{-f} stops the assembler from doing whitespace
2102 and comment preprocessing on
2103 the input file(s) before assembling them. @xref{Preprocessing,
2107 @emph{Warning:} if you use @samp{-f} when the files actually need to be
2108 preprocessed (if they contain comments, for example), @command{@value{AS}} does
2113 @section @code{.include} Search Path: @option{-I} @var{path}
2115 @kindex -I @var{path}
2116 @cindex paths for @code{.include}
2117 @cindex search path for @code{.include}
2118 @cindex @code{include} directive search path
2119 Use this option to add a @var{path} to the list of directories
2120 @command{@value{AS}} searches for files specified in @code{.include}
2121 directives (@pxref{Include,,@code{.include}}). You may use @option{-I} as
2122 many times as necessary to include a variety of paths. The current
2123 working directory is always searched first; after that, @command{@value{AS}}
2124 searches any @samp{-I} directories in the same order as they were
2125 specified (left to right) on the command line.
2128 @section Difference Tables: @option{-K}
2131 @ifclear DIFF-TBL-KLUGE
2132 On the @value{TARGET} family, this option is allowed, but has no effect. It is
2133 permitted for compatibility with the @sc{gnu} assembler on other platforms,
2134 where it can be used to warn when the assembler alters the machine code
2135 generated for @samp{.word} directives in difference tables. The @value{TARGET}
2136 family does not have the addressing limitations that sometimes lead to this
2137 alteration on other platforms.
2140 @ifset DIFF-TBL-KLUGE
2141 @cindex difference tables, warning
2142 @cindex warning for altered difference tables
2143 @command{@value{AS}} sometimes alters the code emitted for directives of the
2144 form @samp{.word @var{sym1}-@var{sym2}}. @xref{Word,,@code{.word}}.
2145 You can use the @samp{-K} option if you want a warning issued when this
2150 @section Include Local Symbols: @option{-L}
2153 @cindex local symbols, retaining in output
2154 Symbols beginning with system-specific local label prefixes, typically
2155 @samp{.L} for ELF systems or @samp{L} for traditional a.out systems, are
2156 called @dfn{local symbols}. @xref{Symbol Names}. Normally you do not see
2157 such symbols when debugging, because they are intended for the use of
2158 programs (like compilers) that compose assembler programs, not for your
2159 notice. Normally both @command{@value{AS}} and @code{@value{LD}} discard
2160 such symbols, so you do not normally debug with them.
2162 This option tells @command{@value{AS}} to retain those local symbols
2163 in the object file. Usually if you do this you also tell the linker
2164 @code{@value{LD}} to preserve those symbols.
2167 @section Configuring listing output: @option{--listing}
2169 The listing feature of the assembler can be enabled via the command line switch
2170 @samp{-a} (@pxref{a}). This feature combines the input source file(s) with a
2171 hex dump of the corresponding locations in the output object file, and displays
2172 them as a listing file. The format of this listing can be controlled by
2173 directives inside the assembler source (i.e., @code{.list} (@pxref{List}),
2174 @code{.title} (@pxref{Title}), @code{.sbttl} (@pxref{Sbttl}),
2175 @code{.psize} (@pxref{Psize}), and
2176 @code{.eject} (@pxref{Eject}) and also by the following switches:
2179 @item --listing-lhs-width=@samp{number}
2180 @kindex --listing-lhs-width
2181 @cindex Width of first line disassembly output
2182 Sets the maximum width, in words, of the first line of the hex byte dump. This
2183 dump appears on the left hand side of the listing output.
2185 @item --listing-lhs-width2=@samp{number}
2186 @kindex --listing-lhs-width2
2187 @cindex Width of continuation lines of disassembly output
2188 Sets the maximum width, in words, of any further lines of the hex byte dump for
2189 a given input source line. If this value is not specified, it defaults to being
2190 the same as the value specified for @samp{--listing-lhs-width}. If neither
2191 switch is used the default is to one.
2193 @item --listing-rhs-width=@samp{number}
2194 @kindex --listing-rhs-width
2195 @cindex Width of source line output
2196 Sets the maximum width, in characters, of the source line that is displayed
2197 alongside the hex dump. The default value for this parameter is 100. The
2198 source line is displayed on the right hand side of the listing output.
2200 @item --listing-cont-lines=@samp{number}
2201 @kindex --listing-cont-lines
2202 @cindex Maximum number of continuation lines
2203 Sets the maximum number of continuation lines of hex dump that will be
2204 displayed for a given single line of source input. The default value is 4.
2208 @section Assemble in MRI Compatibility Mode: @option{-M}
2211 @cindex MRI compatibility mode
2212 The @option{-M} or @option{--mri} option selects MRI compatibility mode. This
2213 changes the syntax and pseudo-op handling of @command{@value{AS}} to make it
2214 compatible with the @code{ASM68K} or the @code{ASM960} (depending upon the
2215 configured target) assembler from Microtec Research. The exact nature of the
2216 MRI syntax will not be documented here; see the MRI manuals for more
2217 information. Note in particular that the handling of macros and macro
2218 arguments is somewhat different. The purpose of this option is to permit
2219 assembling existing MRI assembler code using @command{@value{AS}}.
2221 The MRI compatibility is not complete. Certain operations of the MRI assembler
2222 depend upon its object file format, and can not be supported using other object
2223 file formats. Supporting these would require enhancing each object file format
2224 individually. These are:
2227 @item global symbols in common section
2229 The m68k MRI assembler supports common sections which are merged by the linker.
2230 Other object file formats do not support this. @command{@value{AS}} handles
2231 common sections by treating them as a single common symbol. It permits local
2232 symbols to be defined within a common section, but it can not support global
2233 symbols, since it has no way to describe them.
2235 @item complex relocations
2237 The MRI assemblers support relocations against a negated section address, and
2238 relocations which combine the start addresses of two or more sections. These
2239 are not support by other object file formats.
2241 @item @code{END} pseudo-op specifying start address
2243 The MRI @code{END} pseudo-op permits the specification of a start address.
2244 This is not supported by other object file formats. The start address may
2245 instead be specified using the @option{-e} option to the linker, or in a linker
2248 @item @code{IDNT}, @code{.ident} and @code{NAME} pseudo-ops
2250 The MRI @code{IDNT}, @code{.ident} and @code{NAME} pseudo-ops assign a module
2251 name to the output file. This is not supported by other object file formats.
2253 @item @code{ORG} pseudo-op
2255 The m68k MRI @code{ORG} pseudo-op begins an absolute section at a given
2256 address. This differs from the usual @command{@value{AS}} @code{.org} pseudo-op,
2257 which changes the location within the current section. Absolute sections are
2258 not supported by other object file formats. The address of a section may be
2259 assigned within a linker script.
2262 There are some other features of the MRI assembler which are not supported by
2263 @command{@value{AS}}, typically either because they are difficult or because they
2264 seem of little consequence. Some of these may be supported in future releases.
2268 @item EBCDIC strings
2270 EBCDIC strings are not supported.
2272 @item packed binary coded decimal
2274 Packed binary coded decimal is not supported. This means that the @code{DC.P}
2275 and @code{DCB.P} pseudo-ops are not supported.
2277 @item @code{FEQU} pseudo-op
2279 The m68k @code{FEQU} pseudo-op is not supported.
2281 @item @code{NOOBJ} pseudo-op
2283 The m68k @code{NOOBJ} pseudo-op is not supported.
2285 @item @code{OPT} branch control options
2287 The m68k @code{OPT} branch control options---@code{B}, @code{BRS}, @code{BRB},
2288 @code{BRL}, and @code{BRW}---are ignored. @command{@value{AS}} automatically
2289 relaxes all branches, whether forward or backward, to an appropriate size, so
2290 these options serve no purpose.
2292 @item @code{OPT} list control options
2294 The following m68k @code{OPT} list control options are ignored: @code{C},
2295 @code{CEX}, @code{CL}, @code{CRE}, @code{E}, @code{G}, @code{I}, @code{M},
2296 @code{MEX}, @code{MC}, @code{MD}, @code{X}.
2298 @item other @code{OPT} options
2300 The following m68k @code{OPT} options are ignored: @code{NEST}, @code{O},
2301 @code{OLD}, @code{OP}, @code{P}, @code{PCO}, @code{PCR}, @code{PCS}, @code{R}.
2303 @item @code{OPT} @code{D} option is default
2305 The m68k @code{OPT} @code{D} option is the default, unlike the MRI assembler.
2306 @code{OPT NOD} may be used to turn it off.
2308 @item @code{XREF} pseudo-op.
2310 The m68k @code{XREF} pseudo-op is ignored.
2312 @item @code{.debug} pseudo-op
2314 The i960 @code{.debug} pseudo-op is not supported.
2316 @item @code{.extended} pseudo-op
2318 The i960 @code{.extended} pseudo-op is not supported.
2320 @item @code{.list} pseudo-op.
2322 The various options of the i960 @code{.list} pseudo-op are not supported.
2324 @item @code{.optimize} pseudo-op
2326 The i960 @code{.optimize} pseudo-op is not supported.
2328 @item @code{.output} pseudo-op
2330 The i960 @code{.output} pseudo-op is not supported.
2332 @item @code{.setreal} pseudo-op
2334 The i960 @code{.setreal} pseudo-op is not supported.
2339 @section Dependency Tracking: @option{--MD}
2342 @cindex dependency tracking
2345 @command{@value{AS}} can generate a dependency file for the file it creates. This
2346 file consists of a single rule suitable for @code{make} describing the
2347 dependencies of the main source file.
2349 The rule is written to the file named in its argument.
2351 This feature is used in the automatic updating of makefiles.
2354 @section Name the Object File: @option{-o}
2357 @cindex naming object file
2358 @cindex object file name
2359 There is always one object file output when you run @command{@value{AS}}. By
2360 default it has the name
2363 @file{a.out} (or @file{b.out}, for Intel 960 targets only).
2377 You use this option (which takes exactly one filename) to give the
2378 object file a different name.
2380 Whatever the object file is called, @command{@value{AS}} overwrites any
2381 existing file of the same name.
2384 @section Join Data and Text Sections: @option{-R}
2387 @cindex data and text sections, joining
2388 @cindex text and data sections, joining
2389 @cindex joining text and data sections
2390 @cindex merging text and data sections
2391 @option{-R} tells @command{@value{AS}} to write the object file as if all
2392 data-section data lives in the text section. This is only done at
2393 the very last moment: your binary data are the same, but data
2394 section parts are relocated differently. The data section part of
2395 your object file is zero bytes long because all its bytes are
2396 appended to the text section. (@xref{Sections,,Sections and Relocation}.)
2398 When you specify @option{-R} it would be possible to generate shorter
2399 address displacements (because we do not have to cross between text and
2400 data section). We refrain from doing this simply for compatibility with
2401 older versions of @command{@value{AS}}. In future, @option{-R} may work this way.
2404 When @command{@value{AS}} is configured for COFF or ELF output,
2405 this option is only useful if you use sections named @samp{.text} and
2410 @option{-R} is not supported for any of the HPPA targets. Using
2411 @option{-R} generates a warning from @command{@value{AS}}.
2415 @section Display Assembly Statistics: @option{--statistics}
2417 @kindex --statistics
2418 @cindex statistics, about assembly
2419 @cindex time, total for assembly
2420 @cindex space used, maximum for assembly
2421 Use @samp{--statistics} to display two statistics about the resources used by
2422 @command{@value{AS}}: the maximum amount of space allocated during the assembly
2423 (in bytes), and the total execution time taken for the assembly (in @sc{cpu}
2426 @node traditional-format
2427 @section Compatible Output: @option{--traditional-format}
2429 @kindex --traditional-format
2430 For some targets, the output of @command{@value{AS}} is different in some ways
2431 from the output of some existing assembler. This switch requests
2432 @command{@value{AS}} to use the traditional format instead.
2434 For example, it disables the exception frame optimizations which
2435 @command{@value{AS}} normally does by default on @code{@value{GCC}} output.
2438 @section Announce Version: @option{-v}
2442 @cindex assembler version
2443 @cindex version of assembler
2444 You can find out what version of as is running by including the
2445 option @samp{-v} (which you can also spell as @samp{-version}) on the
2449 @section Control Warnings: @option{-W}, @option{--warn}, @option{--no-warn}, @option{--fatal-warnings}
2451 @command{@value{AS}} should never give a warning or error message when
2452 assembling compiler output. But programs written by people often
2453 cause @command{@value{AS}} to give a warning that a particular assumption was
2454 made. All such warnings are directed to the standard error file.
2458 @cindex suppressing warnings
2459 @cindex warnings, suppressing
2460 If you use the @option{-W} and @option{--no-warn} options, no warnings are issued.
2461 This only affects the warning messages: it does not change any particular of
2462 how @command{@value{AS}} assembles your file. Errors, which stop the assembly,
2465 @kindex --fatal-warnings
2466 @cindex errors, caused by warnings
2467 @cindex warnings, causing error
2468 If you use the @option{--fatal-warnings} option, @command{@value{AS}} considers
2469 files that generate warnings to be in error.
2472 @cindex warnings, switching on
2473 You can switch these options off again by specifying @option{--warn}, which
2474 causes warnings to be output as usual.
2477 @section Generate Object File in Spite of Errors: @option{-Z}
2478 @cindex object file, after errors
2479 @cindex errors, continuing after
2480 After an error message, @command{@value{AS}} normally produces no output. If for
2481 some reason you are interested in object file output even after
2482 @command{@value{AS}} gives an error message on your program, use the @samp{-Z}
2483 option. If there are any errors, @command{@value{AS}} continues anyways, and
2484 writes an object file after a final warning message of the form @samp{@var{n}
2485 errors, @var{m} warnings, generating bad object file.}
2490 @cindex machine-independent syntax
2491 @cindex syntax, machine-independent
2492 This chapter describes the machine-independent syntax allowed in a
2493 source file. @command{@value{AS}} syntax is similar to what many other
2494 assemblers use; it is inspired by the BSD 4.2
2499 assembler, except that @command{@value{AS}} does not assemble Vax bit-fields.
2503 * Preprocessing:: Preprocessing
2504 * Whitespace:: Whitespace
2505 * Comments:: Comments
2506 * Symbol Intro:: Symbols
2507 * Statements:: Statements
2508 * Constants:: Constants
2512 @section Preprocessing
2514 @cindex preprocessing
2515 The @command{@value{AS}} internal preprocessor:
2517 @cindex whitespace, removed by preprocessor
2519 adjusts and removes extra whitespace. It leaves one space or tab before
2520 the keywords on a line, and turns any other whitespace on the line into
2523 @cindex comments, removed by preprocessor
2525 removes all comments, replacing them with a single space, or an
2526 appropriate number of newlines.
2528 @cindex constants, converted by preprocessor
2530 converts character constants into the appropriate numeric values.
2533 It does not do macro processing, include file handling, or
2534 anything else you may get from your C compiler's preprocessor. You can
2535 do include file processing with the @code{.include} directive
2536 (@pxref{Include,,@code{.include}}). You can use the @sc{gnu} C compiler driver
2537 to get other ``CPP'' style preprocessing by giving the input file a
2538 @samp{.S} suffix. @xref{Overall Options, ,Options Controlling the Kind of
2539 Output, gcc.info, Using GNU CC}.
2541 Excess whitespace, comments, and character constants
2542 cannot be used in the portions of the input text that are not
2545 @cindex turning preprocessing on and off
2546 @cindex preprocessing, turning on and off
2549 If the first line of an input file is @code{#NO_APP} or if you use the
2550 @samp{-f} option, whitespace and comments are not removed from the input file.
2551 Within an input file, you can ask for whitespace and comment removal in
2552 specific portions of the by putting a line that says @code{#APP} before the
2553 text that may contain whitespace or comments, and putting a line that says
2554 @code{#NO_APP} after this text. This feature is mainly intend to support
2555 @code{asm} statements in compilers whose output is otherwise free of comments
2562 @dfn{Whitespace} is one or more blanks or tabs, in any order.
2563 Whitespace is used to separate symbols, and to make programs neater for
2564 people to read. Unless within character constants
2565 (@pxref{Characters,,Character Constants}), any whitespace means the same
2566 as exactly one space.
2572 There are two ways of rendering comments to @command{@value{AS}}. In both
2573 cases the comment is equivalent to one space.
2575 Anything from @samp{/*} through the next @samp{*/} is a comment.
2576 This means you may not nest these comments.
2580 The only way to include a newline ('\n') in a comment
2581 is to use this sort of comment.
2584 /* This sort of comment does not nest. */
2587 @cindex line comment character
2588 Anything from a @dfn{line comment} character up to the next newline is
2589 considered a comment and is ignored. The line comment character is target
2590 specific, and some targets multiple comment characters. Some targets also have
2591 line comment characters that only work if they are the first character on a
2592 line. Some targets use a sequence of two characters to introduce a line
2593 comment. Some targets can also change their line comment characters depending
2594 upon command line options that have been used. For more details see the
2595 @emph{Syntax} section in the documentation for individual targets.
2597 If the line comment character is the hash sign (@samp{#}) then it still has the
2598 special ability to enable and disable preprocessing (@pxref{Preprocessing}) and
2599 to specify logical line numbers:
2602 @cindex lines starting with @code{#}
2603 @cindex logical line numbers
2604 To be compatible with past assemblers, lines that begin with @samp{#} have a
2605 special interpretation. Following the @samp{#} should be an absolute
2606 expression (@pxref{Expressions}): the logical line number of the @emph{next}
2607 line. Then a string (@pxref{Strings, ,Strings}) is allowed: if present it is a
2608 new logical file name. The rest of the line, if any, should be whitespace.
2610 If the first non-whitespace characters on the line are not numeric,
2611 the line is ignored. (Just like a comment.)
2614 # This is an ordinary comment.
2615 # 42-6 "new_file_name" # New logical file name
2616 # This is logical line # 36.
2618 This feature is deprecated, and may disappear from future versions
2619 of @command{@value{AS}}.
2624 @cindex characters used in symbols
2625 @ifclear SPECIAL-SYMS
2626 A @dfn{symbol} is one or more characters chosen from the set of all
2627 letters (both upper and lower case), digits and the three characters
2633 A @dfn{symbol} is one or more characters chosen from the set of all
2634 letters (both upper and lower case), digits and the three characters
2635 @samp{._$}. (Save that, on the H8/300 only, you may not use @samp{$} in
2641 On most machines, you can also use @code{$} in symbol names; exceptions
2642 are noted in @ref{Machine Dependencies}.
2644 No symbol may begin with a digit. Case is significant.
2645 There is no length limit: all characters are significant. Multibyte characters
2646 are supported. Symbols are delimited by characters not in that set, or by the
2647 beginning of a file (since the source program must end with a newline, the end
2648 of a file is not a possible symbol delimiter). @xref{Symbols}.
2649 @cindex length of symbols
2654 @cindex statements, structure of
2655 @cindex line separator character
2656 @cindex statement separator character
2658 A @dfn{statement} ends at a newline character (@samp{\n}) or a
2659 @dfn{line separator character}. The line separator character is target
2660 specific and described in the @emph{Syntax} section of each
2661 target's documentation. Not all targets support a line separator character.
2662 The newline or line separator character is considered to be part of the
2663 preceding statement. Newlines and separators within character constants are an
2664 exception: they do not end statements.
2666 @cindex newline, required at file end
2667 @cindex EOF, newline must precede
2668 It is an error to end any statement with end-of-file: the last
2669 character of any input file should be a newline.@refill
2671 An empty statement is allowed, and may include whitespace. It is ignored.
2673 @cindex instructions and directives
2674 @cindex directives and instructions
2675 @c "key symbol" is not used elsewhere in the document; seems pedantic to
2676 @c @defn{} it in that case, as was done previously... doc@cygnus.com,
2678 A statement begins with zero or more labels, optionally followed by a
2679 key symbol which determines what kind of statement it is. The key
2680 symbol determines the syntax of the rest of the statement. If the
2681 symbol begins with a dot @samp{.} then the statement is an assembler
2682 directive: typically valid for any computer. If the symbol begins with
2683 a letter the statement is an assembly language @dfn{instruction}: it
2684 assembles into a machine language instruction.
2686 Different versions of @command{@value{AS}} for different computers
2687 recognize different instructions. In fact, the same symbol may
2688 represent a different instruction in a different computer's assembly
2692 @cindex @code{:} (label)
2693 @cindex label (@code{:})
2694 A label is a symbol immediately followed by a colon (@code{:}).
2695 Whitespace before a label or after a colon is permitted, but you may not
2696 have whitespace between a label's symbol and its colon. @xref{Labels}.
2699 For HPPA targets, labels need not be immediately followed by a colon, but
2700 the definition of a label must begin in column zero. This also implies that
2701 only one label may be defined on each line.
2705 label: .directive followed by something
2706 another_label: # This is an empty statement.
2707 instruction operand_1, operand_2, @dots{}
2714 A constant is a number, written so that its value is known by
2715 inspection, without knowing any context. Like this:
2718 .byte 74, 0112, 092, 0x4A, 0X4a, 'J, '\J # All the same value.
2719 .ascii "Ring the bell\7" # A string constant.
2720 .octa 0x123456789abcdef0123456789ABCDEF0 # A bignum.
2721 .float 0f-314159265358979323846264338327\
2722 95028841971.693993751E-40 # - pi, a flonum.
2727 * Characters:: Character Constants
2728 * Numbers:: Number Constants
2732 @subsection Character Constants
2734 @cindex character constants
2735 @cindex constants, character
2736 There are two kinds of character constants. A @dfn{character} stands
2737 for one character in one byte and its value may be used in
2738 numeric expressions. String constants (properly called string
2739 @emph{literals}) are potentially many bytes and their values may not be
2740 used in arithmetic expressions.
2744 * Chars:: Characters
2748 @subsubsection Strings
2750 @cindex string constants
2751 @cindex constants, string
2752 A @dfn{string} is written between double-quotes. It may contain
2753 double-quotes or null characters. The way to get special characters
2754 into a string is to @dfn{escape} these characters: precede them with
2755 a backslash @samp{\} character. For example @samp{\\} represents
2756 one backslash: the first @code{\} is an escape which tells
2757 @command{@value{AS}} to interpret the second character literally as a backslash
2758 (which prevents @command{@value{AS}} from recognizing the second @code{\} as an
2759 escape character). The complete list of escapes follows.
2761 @cindex escape codes, character
2762 @cindex character escape codes
2765 @c Mnemonic for ACKnowledge; for ASCII this is octal code 007.
2767 @cindex @code{\b} (backspace character)
2768 @cindex backspace (@code{\b})
2770 Mnemonic for backspace; for ASCII this is octal code 010.
2773 @c Mnemonic for EOText; for ASCII this is octal code 004.
2775 @cindex @code{\f} (formfeed character)
2776 @cindex formfeed (@code{\f})
2778 Mnemonic for FormFeed; for ASCII this is octal code 014.
2780 @cindex @code{\n} (newline character)
2781 @cindex newline (@code{\n})
2783 Mnemonic for newline; for ASCII this is octal code 012.
2786 @c Mnemonic for prefix; for ASCII this is octal code 033, usually known as @code{escape}.
2788 @cindex @code{\r} (carriage return character)
2789 @cindex carriage return (@code{\r})
2791 Mnemonic for carriage-Return; for ASCII this is octal code 015.
2794 @c Mnemonic for space; for ASCII this is octal code 040. Included for compliance with
2795 @c other assemblers.
2797 @cindex @code{\t} (tab)
2798 @cindex tab (@code{\t})
2800 Mnemonic for horizontal Tab; for ASCII this is octal code 011.
2803 @c Mnemonic for Vertical tab; for ASCII this is octal code 013.
2804 @c @item \x @var{digit} @var{digit} @var{digit}
2805 @c A hexadecimal character code. The numeric code is 3 hexadecimal digits.
2807 @cindex @code{\@var{ddd}} (octal character code)
2808 @cindex octal character code (@code{\@var{ddd}})
2809 @item \ @var{digit} @var{digit} @var{digit}
2810 An octal character code. The numeric code is 3 octal digits.
2811 For compatibility with other Unix systems, 8 and 9 are accepted as digits:
2812 for example, @code{\008} has the value 010, and @code{\009} the value 011.
2814 @cindex @code{\@var{xd...}} (hex character code)
2815 @cindex hex character code (@code{\@var{xd...}})
2816 @item \@code{x} @var{hex-digits...}
2817 A hex character code. All trailing hex digits are combined. Either upper or
2818 lower case @code{x} works.
2820 @cindex @code{\\} (@samp{\} character)
2821 @cindex backslash (@code{\\})
2823 Represents one @samp{\} character.
2826 @c Represents one @samp{'} (accent acute) character.
2827 @c This is needed in single character literals
2828 @c (@xref{Characters,,Character Constants}.) to represent
2831 @cindex @code{\"} (doublequote character)
2832 @cindex doublequote (@code{\"})
2834 Represents one @samp{"} character. Needed in strings to represent
2835 this character, because an unescaped @samp{"} would end the string.
2837 @item \ @var{anything-else}
2838 Any other character when escaped by @kbd{\} gives a warning, but
2839 assembles as if the @samp{\} was not present. The idea is that if
2840 you used an escape sequence you clearly didn't want the literal
2841 interpretation of the following character. However @command{@value{AS}} has no
2842 other interpretation, so @command{@value{AS}} knows it is giving you the wrong
2843 code and warns you of the fact.
2846 Which characters are escapable, and what those escapes represent,
2847 varies widely among assemblers. The current set is what we think
2848 the BSD 4.2 assembler recognizes, and is a subset of what most C
2849 compilers recognize. If you are in doubt, do not use an escape
2853 @subsubsection Characters
2855 @cindex single character constant
2856 @cindex character, single
2857 @cindex constant, single character
2858 A single character may be written as a single quote immediately
2859 followed by that character. The same escapes apply to characters as
2860 to strings. So if you want to write the character backslash, you
2861 must write @kbd{'\\} where the first @code{\} escapes the second
2862 @code{\}. As you can see, the quote is an acute accent, not a
2863 grave accent. A newline
2865 @ifclear abnormal-separator
2866 (or semicolon @samp{;})
2868 @ifset abnormal-separator
2870 (or dollar sign @samp{$}, for the H8/300; or semicolon @samp{;} for the
2875 immediately following an acute accent is taken as a literal character
2876 and does not count as the end of a statement. The value of a character
2877 constant in a numeric expression is the machine's byte-wide code for
2878 that character. @command{@value{AS}} assumes your character code is ASCII:
2879 @kbd{'A} means 65, @kbd{'B} means 66, and so on. @refill
2882 @subsection Number Constants
2884 @cindex constants, number
2885 @cindex number constants
2886 @command{@value{AS}} distinguishes three kinds of numbers according to how they
2887 are stored in the target machine. @emph{Integers} are numbers that
2888 would fit into an @code{int} in the C language. @emph{Bignums} are
2889 integers, but they are stored in more than 32 bits. @emph{Flonums}
2890 are floating point numbers, described below.
2893 * Integers:: Integers
2898 * Bit Fields:: Bit Fields
2904 @subsubsection Integers
2906 @cindex constants, integer
2908 @cindex binary integers
2909 @cindex integers, binary
2910 A binary integer is @samp{0b} or @samp{0B} followed by zero or more of
2911 the binary digits @samp{01}.
2913 @cindex octal integers
2914 @cindex integers, octal
2915 An octal integer is @samp{0} followed by zero or more of the octal
2916 digits (@samp{01234567}).
2918 @cindex decimal integers
2919 @cindex integers, decimal
2920 A decimal integer starts with a non-zero digit followed by zero or
2921 more digits (@samp{0123456789}).
2923 @cindex hexadecimal integers
2924 @cindex integers, hexadecimal
2925 A hexadecimal integer is @samp{0x} or @samp{0X} followed by one or
2926 more hexadecimal digits chosen from @samp{0123456789abcdefABCDEF}.
2928 Integers have the usual values. To denote a negative integer, use
2929 the prefix operator @samp{-} discussed under expressions
2930 (@pxref{Prefix Ops,,Prefix Operators}).
2933 @subsubsection Bignums
2936 @cindex constants, bignum
2937 A @dfn{bignum} has the same syntax and semantics as an integer
2938 except that the number (or its negative) takes more than 32 bits to
2939 represent in binary. The distinction is made because in some places
2940 integers are permitted while bignums are not.
2943 @subsubsection Flonums
2945 @cindex floating point numbers
2946 @cindex constants, floating point
2948 @cindex precision, floating point
2949 A @dfn{flonum} represents a floating point number. The translation is
2950 indirect: a decimal floating point number from the text is converted by
2951 @command{@value{AS}} to a generic binary floating point number of more than
2952 sufficient precision. This generic floating point number is converted
2953 to a particular computer's floating point format (or formats) by a
2954 portion of @command{@value{AS}} specialized to that computer.
2956 A flonum is written by writing (in order)
2961 (@samp{0} is optional on the HPPA.)
2965 A letter, to tell @command{@value{AS}} the rest of the number is a flonum.
2967 @kbd{e} is recommended. Case is not important.
2969 @c FIXME: verify if flonum syntax really this vague for most cases
2970 (Any otherwise illegal letter works here, but that might be changed. Vax BSD
2971 4.2 assembler seems to allow any of @samp{defghDEFGH}.)
2974 On the H8/300, Renesas / SuperH SH,
2975 and AMD 29K architectures, the letter must be
2976 one of the letters @samp{DFPRSX} (in upper or lower case).
2978 On the ARC, the letter must be one of the letters @samp{DFRS}
2979 (in upper or lower case).
2981 On the Intel 960 architecture, the letter must be
2982 one of the letters @samp{DFT} (in upper or lower case).
2984 On the HPPA architecture, the letter must be @samp{E} (upper case only).
2988 One of the letters @samp{DFRS} (in upper or lower case).
2991 One of the letters @samp{DFPRSX} (in upper or lower case).
2994 The letter @samp{E} (upper case only).
2997 One of the letters @samp{DFT} (in upper or lower case).
3002 An optional sign: either @samp{+} or @samp{-}.
3005 An optional @dfn{integer part}: zero or more decimal digits.
3008 An optional @dfn{fractional part}: @samp{.} followed by zero
3009 or more decimal digits.
3012 An optional exponent, consisting of:
3016 An @samp{E} or @samp{e}.
3017 @c I can't find a config where "EXP_CHARS" is other than 'eE', but in
3018 @c principle this can perfectly well be different on different targets.
3020 Optional sign: either @samp{+} or @samp{-}.
3022 One or more decimal digits.
3027 At least one of the integer part or the fractional part must be
3028 present. The floating point number has the usual base-10 value.
3030 @command{@value{AS}} does all processing using integers. Flonums are computed
3031 independently of any floating point hardware in the computer running
3032 @command{@value{AS}}.
3036 @c Bit fields are written as a general facility but are also controlled
3037 @c by a conditional-compilation flag---which is as of now (21mar91)
3038 @c turned on only by the i960 config of GAS.
3040 @subsubsection Bit Fields
3043 @cindex constants, bit field
3044 You can also define numeric constants as @dfn{bit fields}.
3045 Specify two numbers separated by a colon---
3047 @var{mask}:@var{value}
3050 @command{@value{AS}} applies a bitwise @sc{and} between @var{mask} and
3053 The resulting number is then packed
3055 @c this conditional paren in case bit fields turned on elsewhere than 960
3056 (in host-dependent byte order)
3058 into a field whose width depends on which assembler directive has the
3059 bit-field as its argument. Overflow (a result from the bitwise and
3060 requiring more binary digits to represent) is not an error; instead,
3061 more constants are generated, of the specified width, beginning with the
3062 least significant digits.@refill
3064 The directives @code{.byte}, @code{.hword}, @code{.int}, @code{.long},
3065 @code{.short}, and @code{.word} accept bit-field arguments.
3070 @chapter Sections and Relocation
3075 * Secs Background:: Background
3076 * Ld Sections:: Linker Sections
3077 * As Sections:: Assembler Internal Sections
3078 * Sub-Sections:: Sub-Sections
3082 @node Secs Background
3085 Roughly, a section is a range of addresses, with no gaps; all data
3086 ``in'' those addresses is treated the same for some particular purpose.
3087 For example there may be a ``read only'' section.
3089 @cindex linker, and assembler
3090 @cindex assembler, and linker
3091 The linker @code{@value{LD}} reads many object files (partial programs) and
3092 combines their contents to form a runnable program. When @command{@value{AS}}
3093 emits an object file, the partial program is assumed to start at address 0.
3094 @code{@value{LD}} assigns the final addresses for the partial program, so that
3095 different partial programs do not overlap. This is actually an
3096 oversimplification, but it suffices to explain how @command{@value{AS}} uses
3099 @code{@value{LD}} moves blocks of bytes of your program to their run-time
3100 addresses. These blocks slide to their run-time addresses as rigid
3101 units; their length does not change and neither does the order of bytes
3102 within them. Such a rigid unit is called a @emph{section}. Assigning
3103 run-time addresses to sections is called @dfn{relocation}. It includes
3104 the task of adjusting mentions of object-file addresses so they refer to
3105 the proper run-time addresses.
3107 For the H8/300, and for the Renesas / SuperH SH,
3108 @command{@value{AS}} pads sections if needed to
3109 ensure they end on a word (sixteen bit) boundary.
3112 @cindex standard assembler sections
3113 An object file written by @command{@value{AS}} has at least three sections, any
3114 of which may be empty. These are named @dfn{text}, @dfn{data} and
3119 When it generates COFF or ELF output,
3121 @command{@value{AS}} can also generate whatever other named sections you specify
3122 using the @samp{.section} directive (@pxref{Section,,@code{.section}}).
3123 If you do not use any directives that place output in the @samp{.text}
3124 or @samp{.data} sections, these sections still exist, but are empty.
3129 When @command{@value{AS}} generates SOM or ELF output for the HPPA,
3131 @command{@value{AS}} can also generate whatever other named sections you
3132 specify using the @samp{.space} and @samp{.subspace} directives. See
3133 @cite{HP9000 Series 800 Assembly Language Reference Manual}
3134 (HP 92432-90001) for details on the @samp{.space} and @samp{.subspace}
3135 assembler directives.
3138 Additionally, @command{@value{AS}} uses different names for the standard
3139 text, data, and bss sections when generating SOM output. Program text
3140 is placed into the @samp{$CODE$} section, data into @samp{$DATA$}, and
3141 BSS into @samp{$BSS$}.
3145 Within the object file, the text section starts at address @code{0}, the
3146 data section follows, and the bss section follows the data section.
3149 When generating either SOM or ELF output files on the HPPA, the text
3150 section starts at address @code{0}, the data section at address
3151 @code{0x4000000}, and the bss section follows the data section.
3154 To let @code{@value{LD}} know which data changes when the sections are
3155 relocated, and how to change that data, @command{@value{AS}} also writes to the
3156 object file details of the relocation needed. To perform relocation
3157 @code{@value{LD}} must know, each time an address in the object
3161 Where in the object file is the beginning of this reference to
3164 How long (in bytes) is this reference?
3166 Which section does the address refer to? What is the numeric value of
3168 (@var{address}) @minus{} (@var{start-address of section})?
3171 Is the reference to an address ``Program-Counter relative''?
3174 @cindex addresses, format of
3175 @cindex section-relative addressing
3176 In fact, every address @command{@value{AS}} ever uses is expressed as
3178 (@var{section}) + (@var{offset into section})
3181 Further, most expressions @command{@value{AS}} computes have this section-relative
3184 (For some object formats, such as SOM for the HPPA, some expressions are
3185 symbol-relative instead.)
3188 In this manual we use the notation @{@var{secname} @var{N}@} to mean ``offset
3189 @var{N} into section @var{secname}.''
3191 Apart from text, data and bss sections you need to know about the
3192 @dfn{absolute} section. When @code{@value{LD}} mixes partial programs,
3193 addresses in the absolute section remain unchanged. For example, address
3194 @code{@{absolute 0@}} is ``relocated'' to run-time address 0 by
3195 @code{@value{LD}}. Although the linker never arranges two partial programs'
3196 data sections with overlapping addresses after linking, @emph{by definition}
3197 their absolute sections must overlap. Address @code{@{absolute@ 239@}} in one
3198 part of a program is always the same address when the program is running as
3199 address @code{@{absolute@ 239@}} in any other part of the program.
3201 The idea of sections is extended to the @dfn{undefined} section. Any
3202 address whose section is unknown at assembly time is by definition
3203 rendered @{undefined @var{U}@}---where @var{U} is filled in later.
3204 Since numbers are always defined, the only way to generate an undefined
3205 address is to mention an undefined symbol. A reference to a named
3206 common block would be such a symbol: its value is unknown at assembly
3207 time so it has section @emph{undefined}.
3209 By analogy the word @emph{section} is used to describe groups of sections in
3210 the linked program. @code{@value{LD}} puts all partial programs' text
3211 sections in contiguous addresses in the linked program. It is
3212 customary to refer to the @emph{text section} of a program, meaning all
3213 the addresses of all partial programs' text sections. Likewise for
3214 data and bss sections.
3216 Some sections are manipulated by @code{@value{LD}}; others are invented for
3217 use of @command{@value{AS}} and have no meaning except during assembly.
3220 @section Linker Sections
3221 @code{@value{LD}} deals with just four kinds of sections, summarized below.
3226 @cindex named sections
3227 @cindex sections, named
3228 @item named sections
3231 @cindex text section
3232 @cindex data section
3236 These sections hold your program. @command{@value{AS}} and @code{@value{LD}} treat them as
3237 separate but equal sections. Anything you can say of one section is
3240 When the program is running, however, it is
3241 customary for the text section to be unalterable. The
3242 text section is often shared among processes: it contains
3243 instructions, constants and the like. The data section of a running
3244 program is usually alterable: for example, C variables would be stored
3245 in the data section.
3250 This section contains zeroed bytes when your program begins running. It
3251 is used to hold uninitialized variables or common storage. The length of
3252 each partial program's bss section is important, but because it starts
3253 out containing zeroed bytes there is no need to store explicit zero
3254 bytes in the object file. The bss section was invented to eliminate
3255 those explicit zeros from object files.
3257 @cindex absolute section
3258 @item absolute section
3259 Address 0 of this section is always ``relocated'' to runtime address 0.
3260 This is useful if you want to refer to an address that @code{@value{LD}} must
3261 not change when relocating. In this sense we speak of absolute
3262 addresses being ``unrelocatable'': they do not change during relocation.
3264 @cindex undefined section
3265 @item undefined section
3266 This ``section'' is a catch-all for address references to objects not in
3267 the preceding sections.
3268 @c FIXME: ref to some other doc on obj-file formats could go here.
3271 @cindex relocation example
3272 An idealized example of three relocatable sections follows.
3274 The example uses the traditional section names @samp{.text} and @samp{.data}.
3276 Memory addresses are on the horizontal axis.
3280 @c END TEXI2ROFF-KILL
3283 partial program # 1: |ttttt|dddd|00|
3290 partial program # 2: |TTT|DDD|000|
3293 +--+---+-----+--+----+---+-----+~~
3294 linked program: | |TTT|ttttt| |dddd|DDD|00000|
3295 +--+---+-----+--+----+---+-----+~~
3297 addresses: 0 @dots{}
3304 \line{\it Partial program \#1: \hfil}
3305 \line{\ibox{2.5cm}{\tt text}\ibox{2cm}{\tt data}\ibox{1cm}{\tt bss}\hfil}
3306 \line{\boxit{2.5cm}{\tt ttttt}\boxit{2cm}{\tt dddd}\boxit{1cm}{\tt 00}\hfil}
3308 \line{\it Partial program \#2: \hfil}
3309 \line{\ibox{1cm}{\tt text}\ibox{1.5cm}{\tt data}\ibox{1cm}{\tt bss}\hfil}
3310 \line{\boxit{1cm}{\tt TTT}\boxit{1.5cm}{\tt DDDD}\boxit{1cm}{\tt 000}\hfil}
3312 \line{\it linked program: \hfil}
3313 \line{\ibox{.5cm}{}\ibox{1cm}{\tt text}\ibox{2.5cm}{}\ibox{.75cm}{}\ibox{2cm}{\tt data}\ibox{1.5cm}{}\ibox{2cm}{\tt bss}\hfil}
3314 \line{\boxit{.5cm}{}\boxit{1cm}{\tt TTT}\boxit{2.5cm}{\tt
3315 ttttt}\boxit{.75cm}{}\boxit{2cm}{\tt dddd}\boxit{1.5cm}{\tt
3316 DDDD}\boxit{2cm}{\tt 00000}\ \dots\hfil}
3318 \line{\it addresses: \hfil}
3322 @c END TEXI2ROFF-KILL
3325 @section Assembler Internal Sections
3327 @cindex internal assembler sections
3328 @cindex sections in messages, internal
3329 These sections are meant only for the internal use of @command{@value{AS}}. They
3330 have no meaning at run-time. You do not really need to know about these
3331 sections for most purposes; but they can be mentioned in @command{@value{AS}}
3332 warning messages, so it might be helpful to have an idea of their
3333 meanings to @command{@value{AS}}. These sections are used to permit the
3334 value of every expression in your assembly language program to be a
3335 section-relative address.
3338 @cindex assembler internal logic error
3339 @item ASSEMBLER-INTERNAL-LOGIC-ERROR!
3340 An internal assembler logic error has been found. This means there is a
3341 bug in the assembler.
3343 @cindex expr (internal section)
3345 The assembler stores complex expression internally as combinations of
3346 symbols. When it needs to represent an expression as a symbol, it puts
3347 it in the expr section.
3349 @c FIXME item transfer[t] vector preload
3350 @c FIXME item transfer[t] vector postload
3351 @c FIXME item register
3355 @section Sub-Sections
3357 @cindex numbered subsections
3358 @cindex grouping data
3364 fall into two sections: text and data.
3366 You may have separate groups of
3368 data in named sections
3372 data in named sections
3378 that you want to end up near to each other in the object file, even though they
3379 are not contiguous in the assembler source. @command{@value{AS}} allows you to
3380 use @dfn{subsections} for this purpose. Within each section, there can be
3381 numbered subsections with values from 0 to 8192. Objects assembled into the
3382 same subsection go into the object file together with other objects in the same
3383 subsection. For example, a compiler might want to store constants in the text
3384 section, but might not want to have them interspersed with the program being
3385 assembled. In this case, the compiler could issue a @samp{.text 0} before each
3386 section of code being output, and a @samp{.text 1} before each group of
3387 constants being output.
3389 Subsections are optional. If you do not use subsections, everything
3390 goes in subsection number zero.
3393 Each subsection is zero-padded up to a multiple of four bytes.
3394 (Subsections may be padded a different amount on different flavors
3395 of @command{@value{AS}}.)
3399 On the H8/300 platform, each subsection is zero-padded to a word
3400 boundary (two bytes).
3401 The same is true on the Renesas SH.
3404 @c FIXME section padding (alignment)?
3405 @c Rich Pixley says padding here depends on target obj code format; that
3406 @c doesn't seem particularly useful to say without further elaboration,
3407 @c so for now I say nothing about it. If this is a generic BFD issue,
3408 @c these paragraphs might need to vanish from this manual, and be
3409 @c discussed in BFD chapter of binutils (or some such).
3413 Subsections appear in your object file in numeric order, lowest numbered
3414 to highest. (All this to be compatible with other people's assemblers.)
3415 The object file contains no representation of subsections; @code{@value{LD}} and
3416 other programs that manipulate object files see no trace of them.
3417 They just see all your text subsections as a text section, and all your
3418 data subsections as a data section.
3420 To specify which subsection you want subsequent statements assembled
3421 into, use a numeric argument to specify it, in a @samp{.text
3422 @var{expression}} or a @samp{.data @var{expression}} statement.
3425 When generating COFF output, you
3430 can also use an extra subsection
3431 argument with arbitrary named sections: @samp{.section @var{name},
3436 When generating ELF output, you
3441 can also use the @code{.subsection} directive (@pxref{SubSection})
3442 to specify a subsection: @samp{.subsection @var{expression}}.
3444 @var{Expression} should be an absolute expression
3445 (@pxref{Expressions}). If you just say @samp{.text} then @samp{.text 0}
3446 is assumed. Likewise @samp{.data} means @samp{.data 0}. Assembly
3447 begins in @code{text 0}. For instance:
3449 .text 0 # The default subsection is text 0 anyway.
3450 .ascii "This lives in the first text subsection. *"
3452 .ascii "But this lives in the second text subsection."
3454 .ascii "This lives in the data section,"
3455 .ascii "in the first data subsection."
3457 .ascii "This lives in the first text section,"
3458 .ascii "immediately following the asterisk (*)."
3461 Each section has a @dfn{location counter} incremented by one for every byte
3462 assembled into that section. Because subsections are merely a convenience
3463 restricted to @command{@value{AS}} there is no concept of a subsection location
3464 counter. There is no way to directly manipulate a location counter---but the
3465 @code{.align} directive changes it, and any label definition captures its
3466 current value. The location counter of the section where statements are being
3467 assembled is said to be the @dfn{active} location counter.
3470 @section bss Section
3473 @cindex common variable storage
3474 The bss section is used for local common variable storage.
3475 You may allocate address space in the bss section, but you may
3476 not dictate data to load into it before your program executes. When
3477 your program starts running, all the contents of the bss
3478 section are zeroed bytes.
3480 The @code{.lcomm} pseudo-op defines a symbol in the bss section; see
3481 @ref{Lcomm,,@code{.lcomm}}.
3483 The @code{.comm} pseudo-op may be used to declare a common symbol, which is
3484 another form of uninitialized symbol; see @ref{Comm,,@code{.comm}}.
3487 When assembling for a target which supports multiple sections, such as ELF or
3488 COFF, you may switch into the @code{.bss} section and define symbols as usual;
3489 see @ref{Section,,@code{.section}}. You may only assemble zero values into the
3490 section. Typically the section will only contain symbol definitions and
3491 @code{.skip} directives (@pxref{Skip,,@code{.skip}}).
3498 Symbols are a central concept: the programmer uses symbols to name
3499 things, the linker uses symbols to link, and the debugger uses symbols
3503 @cindex debuggers, and symbol order
3504 @emph{Warning:} @command{@value{AS}} does not place symbols in the object file in
3505 the same order they were declared. This may break some debuggers.
3510 * Setting Symbols:: Giving Symbols Other Values
3511 * Symbol Names:: Symbol Names
3512 * Dot:: The Special Dot Symbol
3513 * Symbol Attributes:: Symbol Attributes
3520 A @dfn{label} is written as a symbol immediately followed by a colon
3521 @samp{:}. The symbol then represents the current value of the
3522 active location counter, and is, for example, a suitable instruction
3523 operand. You are warned if you use the same symbol to represent two
3524 different locations: the first definition overrides any other
3528 On the HPPA, the usual form for a label need not be immediately followed by a
3529 colon, but instead must start in column zero. Only one label may be defined on
3530 a single line. To work around this, the HPPA version of @command{@value{AS}} also
3531 provides a special directive @code{.label} for defining labels more flexibly.
3534 @node Setting Symbols
3535 @section Giving Symbols Other Values
3537 @cindex assigning values to symbols
3538 @cindex symbol values, assigning
3539 A symbol can be given an arbitrary value by writing a symbol, followed
3540 by an equals sign @samp{=}, followed by an expression
3541 (@pxref{Expressions}). This is equivalent to using the @code{.set}
3542 directive. @xref{Set,,@code{.set}}. In the same way, using a double
3543 equals sign @samp{=}@samp{=} here represents an equivalent of the
3544 @code{.eqv} directive. @xref{Eqv,,@code{.eqv}}.
3547 Blackfin does not support symbol assignment with @samp{=}.
3551 @section Symbol Names
3553 @cindex symbol names
3554 @cindex names, symbol
3555 @ifclear SPECIAL-SYMS
3556 Symbol names begin with a letter or with one of @samp{._}. On most
3557 machines, you can also use @code{$} in symbol names; exceptions are
3558 noted in @ref{Machine Dependencies}. That character may be followed by any
3559 string of digits, letters, dollar signs (unless otherwise noted for a
3560 particular target machine), and underscores.
3564 Symbol names begin with a letter or with one of @samp{._}. On the
3565 Renesas SH you can also use @code{$} in symbol names. That
3566 character may be followed by any string of digits, letters, dollar signs (save
3567 on the H8/300), and underscores.
3571 Case of letters is significant: @code{foo} is a different symbol name
3574 Multibyte characters are supported. To generate a symbol name containing
3575 multibyte characters enclose it within double quotes and use escape codes. cf
3576 @xref{Strings}. Generating a multibyte symbol name from a label is not
3577 currently supported.
3579 Each symbol has exactly one name. Each name in an assembly language program
3580 refers to exactly one symbol. You may use that symbol name any number of times
3583 @subheading Local Symbol Names
3585 @cindex local symbol names
3586 @cindex symbol names, local
3587 A local symbol is any symbol beginning with certain local label prefixes.
3588 By default, the local label prefix is @samp{.L} for ELF systems or
3589 @samp{L} for traditional a.out systems, but each target may have its own
3590 set of local label prefixes.
3592 On the HPPA local symbols begin with @samp{L$}.
3595 Local symbols are defined and used within the assembler, but they are
3596 normally not saved in object files. Thus, they are not visible when debugging.
3597 You may use the @samp{-L} option (@pxref{L, ,Include Local Symbols:
3598 @option{-L}}) to retain the local symbols in the object files.
3600 @subheading Local Labels
3602 @cindex local labels
3603 @cindex temporary symbol names
3604 @cindex symbol names, temporary
3605 Local labels help compilers and programmers use names temporarily.
3606 They create symbols which are guaranteed to be unique over the entire scope of
3607 the input source code and which can be referred to by a simple notation.
3608 To define a local label, write a label of the form @samp{@b{N}:} (where @b{N}
3609 represents any positive integer). To refer to the most recent previous
3610 definition of that label write @samp{@b{N}b}, using the same number as when
3611 you defined the label. To refer to the next definition of a local label, write
3612 @samp{@b{N}f}---the @samp{b} stands for ``backwards'' and the @samp{f} stands
3615 There is no restriction on how you can use these labels, and you can reuse them
3616 too. So that it is possible to repeatedly define the same local label (using
3617 the same number @samp{@b{N}}), although you can only refer to the most recently
3618 defined local label of that number (for a backwards reference) or the next
3619 definition of a specific local label for a forward reference. It is also worth
3620 noting that the first 10 local labels (@samp{@b{0:}}@dots{}@samp{@b{9:}}) are
3621 implemented in a slightly more efficient manner than the others.
3632 Which is the equivalent of:
3635 label_1: branch label_3
3636 label_2: branch label_1
3637 label_3: branch label_4
3638 label_4: branch label_3
3641 Local label names are only a notational device. They are immediately
3642 transformed into more conventional symbol names before the assembler uses them.
3643 The symbol names are stored in the symbol table, appear in error messages, and
3644 are optionally emitted to the object file. The names are constructed using
3648 @item @emph{local label prefix}
3649 All local symbols begin with the system-specific local label prefix.
3650 Normally both @command{@value{AS}} and @code{@value{LD}} forget symbols
3651 that start with the local label prefix. These labels are
3652 used for symbols you are never intended to see. If you use the
3653 @samp{-L} option then @command{@value{AS}} retains these symbols in the
3654 object file. If you also instruct @code{@value{LD}} to retain these symbols,
3655 you may use them in debugging.
3658 This is the number that was used in the local label definition. So if the
3659 label is written @samp{55:} then the number is @samp{55}.
3662 This unusual character is included so you do not accidentally invent a symbol
3663 of the same name. The character has ASCII value of @samp{\002} (control-B).
3665 @item @emph{ordinal number}
3666 This is a serial number to keep the labels distinct. The first definition of
3667 @samp{0:} gets the number @samp{1}. The 15th definition of @samp{0:} gets the
3668 number @samp{15}, and so on. Likewise the first definition of @samp{1:} gets
3669 the number @samp{1} and its 15th definition gets @samp{15} as well.
3672 So for example, the first @code{1:} may be named @code{.L1@kbd{C-B}1}, and
3673 the 44th @code{3:} may be named @code{.L3@kbd{C-B}44}.
3675 @subheading Dollar Local Labels
3676 @cindex dollar local symbols
3678 @code{@value{AS}} also supports an even more local form of local labels called
3679 dollar labels. These labels go out of scope (i.e., they become undefined) as
3680 soon as a non-local label is defined. Thus they remain valid for only a small
3681 region of the input source code. Normal local labels, by contrast, remain in
3682 scope for the entire file, or until they are redefined by another occurrence of
3683 the same local label.
3685 Dollar labels are defined in exactly the same way as ordinary local labels,
3686 except that they have a dollar sign suffix to their numeric value, e.g.,
3689 They can also be distinguished from ordinary local labels by their transformed
3690 names which use ASCII character @samp{\001} (control-A) as the magic character
3691 to distinguish them from ordinary labels. For example, the fifth definition of
3692 @samp{6$} may be named @samp{.L6@kbd{C-A}5}.
3695 @section The Special Dot Symbol
3697 @cindex dot (symbol)
3698 @cindex @code{.} (symbol)
3699 @cindex current address
3700 @cindex location counter
3701 The special symbol @samp{.} refers to the current address that
3702 @command{@value{AS}} is assembling into. Thus, the expression @samp{melvin:
3703 .long .} defines @code{melvin} to contain its own address.
3704 Assigning a value to @code{.} is treated the same as a @code{.org}
3706 @ifclear no-space-dir
3707 Thus, the expression @samp{.=.+4} is the same as saying
3711 @node Symbol Attributes
3712 @section Symbol Attributes
3714 @cindex symbol attributes
3715 @cindex attributes, symbol
3716 Every symbol has, as well as its name, the attributes ``Value'' and
3717 ``Type''. Depending on output format, symbols can also have auxiliary
3720 The detailed definitions are in @file{a.out.h}.
3723 If you use a symbol without defining it, @command{@value{AS}} assumes zero for
3724 all these attributes, and probably won't warn you. This makes the
3725 symbol an externally defined symbol, which is generally what you
3729 * Symbol Value:: Value
3730 * Symbol Type:: Type
3733 * a.out Symbols:: Symbol Attributes: @code{a.out}
3737 * a.out Symbols:: Symbol Attributes: @code{a.out}
3740 * a.out Symbols:: Symbol Attributes: @code{a.out}, @code{b.out}
3745 * COFF Symbols:: Symbol Attributes for COFF
3748 * SOM Symbols:: Symbol Attributes for SOM
3755 @cindex value of a symbol
3756 @cindex symbol value
3757 The value of a symbol is (usually) 32 bits. For a symbol which labels a
3758 location in the text, data, bss or absolute sections the value is the
3759 number of addresses from the start of that section to the label.
3760 Naturally for text, data and bss sections the value of a symbol changes
3761 as @code{@value{LD}} changes section base addresses during linking. Absolute
3762 symbols' values do not change during linking: that is why they are
3765 The value of an undefined symbol is treated in a special way. If it is
3766 0 then the symbol is not defined in this assembler source file, and
3767 @code{@value{LD}} tries to determine its value from other files linked into the
3768 same program. You make this kind of symbol simply by mentioning a symbol
3769 name without defining it. A non-zero value represents a @code{.comm}
3770 common declaration. The value is how much common storage to reserve, in
3771 bytes (addresses). The symbol refers to the first address of the
3777 @cindex type of a symbol
3779 The type attribute of a symbol contains relocation (section)
3780 information, any flag settings indicating that a symbol is external, and
3781 (optionally), other information for linkers and debuggers. The exact
3782 format depends on the object-code output format in use.
3787 @c The following avoids a "widow" subsection title. @group would be
3788 @c better if it were available outside examples.
3791 @subsection Symbol Attributes: @code{a.out}, @code{b.out}
3793 @cindex @code{b.out} symbol attributes
3794 @cindex symbol attributes, @code{b.out}
3795 These symbol attributes appear only when @command{@value{AS}} is configured for
3796 one of the Berkeley-descended object output formats---@code{a.out} or
3802 @subsection Symbol Attributes: @code{a.out}
3804 @cindex @code{a.out} symbol attributes
3805 @cindex symbol attributes, @code{a.out}
3811 @subsection Symbol Attributes: @code{a.out}
3813 @cindex @code{a.out} symbol attributes
3814 @cindex symbol attributes, @code{a.out}
3818 * Symbol Desc:: Descriptor
3819 * Symbol Other:: Other
3823 @subsubsection Descriptor
3825 @cindex descriptor, of @code{a.out} symbol
3826 This is an arbitrary 16-bit value. You may establish a symbol's
3827 descriptor value by using a @code{.desc} statement
3828 (@pxref{Desc,,@code{.desc}}). A descriptor value means nothing to
3829 @command{@value{AS}}.
3832 @subsubsection Other
3834 @cindex other attribute, of @code{a.out} symbol
3835 This is an arbitrary 8-bit value. It means nothing to @command{@value{AS}}.
3840 @subsection Symbol Attributes for COFF
3842 @cindex COFF symbol attributes
3843 @cindex symbol attributes, COFF
3845 The COFF format supports a multitude of auxiliary symbol attributes;
3846 like the primary symbol attributes, they are set between @code{.def} and
3847 @code{.endef} directives.
3849 @subsubsection Primary Attributes
3851 @cindex primary attributes, COFF symbols
3852 The symbol name is set with @code{.def}; the value and type,
3853 respectively, with @code{.val} and @code{.type}.
3855 @subsubsection Auxiliary Attributes
3857 @cindex auxiliary attributes, COFF symbols
3858 The @command{@value{AS}} directives @code{.dim}, @code{.line}, @code{.scl},
3859 @code{.size}, @code{.tag}, and @code{.weak} can generate auxiliary symbol
3860 table information for COFF.
3865 @subsection Symbol Attributes for SOM
3867 @cindex SOM symbol attributes
3868 @cindex symbol attributes, SOM
3870 The SOM format for the HPPA supports a multitude of symbol attributes set with
3871 the @code{.EXPORT} and @code{.IMPORT} directives.
3873 The attributes are described in @cite{HP9000 Series 800 Assembly
3874 Language Reference Manual} (HP 92432-90001) under the @code{IMPORT} and
3875 @code{EXPORT} assembler directive documentation.
3879 @chapter Expressions
3883 @cindex numeric values
3884 An @dfn{expression} specifies an address or numeric value.
3885 Whitespace may precede and/or follow an expression.
3887 The result of an expression must be an absolute number, or else an offset into
3888 a particular section. If an expression is not absolute, and there is not
3889 enough information when @command{@value{AS}} sees the expression to know its
3890 section, a second pass over the source program might be necessary to interpret
3891 the expression---but the second pass is currently not implemented.
3892 @command{@value{AS}} aborts with an error message in this situation.
3895 * Empty Exprs:: Empty Expressions
3896 * Integer Exprs:: Integer Expressions
3900 @section Empty Expressions
3902 @cindex empty expressions
3903 @cindex expressions, empty
3904 An empty expression has no value: it is just whitespace or null.
3905 Wherever an absolute expression is required, you may omit the
3906 expression, and @command{@value{AS}} assumes a value of (absolute) 0. This
3907 is compatible with other assemblers.
3910 @section Integer Expressions
3912 @cindex integer expressions
3913 @cindex expressions, integer
3914 An @dfn{integer expression} is one or more @emph{arguments} delimited
3915 by @emph{operators}.
3918 * Arguments:: Arguments
3919 * Operators:: Operators
3920 * Prefix Ops:: Prefix Operators
3921 * Infix Ops:: Infix Operators
3925 @subsection Arguments
3927 @cindex expression arguments
3928 @cindex arguments in expressions
3929 @cindex operands in expressions
3930 @cindex arithmetic operands
3931 @dfn{Arguments} are symbols, numbers or subexpressions. In other
3932 contexts arguments are sometimes called ``arithmetic operands''. In
3933 this manual, to avoid confusing them with the ``instruction operands'' of
3934 the machine language, we use the term ``argument'' to refer to parts of
3935 expressions only, reserving the word ``operand'' to refer only to machine
3936 instruction operands.
3938 Symbols are evaluated to yield @{@var{section} @var{NNN}@} where
3939 @var{section} is one of text, data, bss, absolute,
3940 or undefined. @var{NNN} is a signed, 2's complement 32 bit
3943 Numbers are usually integers.
3945 A number can be a flonum or bignum. In this case, you are warned
3946 that only the low order 32 bits are used, and @command{@value{AS}} pretends
3947 these 32 bits are an integer. You may write integer-manipulating
3948 instructions that act on exotic constants, compatible with other
3951 @cindex subexpressions
3952 Subexpressions are a left parenthesis @samp{(} followed by an integer
3953 expression, followed by a right parenthesis @samp{)}; or a prefix
3954 operator followed by an argument.
3957 @subsection Operators
3959 @cindex operators, in expressions
3960 @cindex arithmetic functions
3961 @cindex functions, in expressions
3962 @dfn{Operators} are arithmetic functions, like @code{+} or @code{%}. Prefix
3963 operators are followed by an argument. Infix operators appear
3964 between their arguments. Operators may be preceded and/or followed by
3968 @subsection Prefix Operator
3970 @cindex prefix operators
3971 @command{@value{AS}} has the following @dfn{prefix operators}. They each take
3972 one argument, which must be absolute.
3974 @c the tex/end tex stuff surrounding this small table is meant to make
3975 @c it align, on the printed page, with the similar table in the next
3976 @c section (which is inside an enumerate).
3978 \global\advance\leftskip by \itemindent
3983 @dfn{Negation}. Two's complement negation.
3985 @dfn{Complementation}. Bitwise not.
3989 \global\advance\leftskip by -\itemindent
3993 @subsection Infix Operators
3995 @cindex infix operators
3996 @cindex operators, permitted arguments
3997 @dfn{Infix operators} take two arguments, one on either side. Operators
3998 have precedence, but operations with equal precedence are performed left
3999 to right. Apart from @code{+} or @option{-}, both arguments must be
4000 absolute, and the result is absolute.
4003 @cindex operator precedence
4004 @cindex precedence of operators
4011 @dfn{Multiplication}.
4014 @dfn{Division}. Truncation is the same as the C operator @samp{/}
4020 @dfn{Shift Left}. Same as the C operator @samp{<<}.
4023 @dfn{Shift Right}. Same as the C operator @samp{>>}.
4027 Intermediate precedence
4032 @dfn{Bitwise Inclusive Or}.
4038 @dfn{Bitwise Exclusive Or}.
4041 @dfn{Bitwise Or Not}.
4048 @cindex addition, permitted arguments
4049 @cindex plus, permitted arguments
4050 @cindex arguments for addition
4052 @dfn{Addition}. If either argument is absolute, the result has the section of
4053 the other argument. You may not add together arguments from different
4056 @cindex subtraction, permitted arguments
4057 @cindex minus, permitted arguments
4058 @cindex arguments for subtraction
4060 @dfn{Subtraction}. If the right argument is absolute, the
4061 result has the section of the left argument.
4062 If both arguments are in the same section, the result is absolute.
4063 You may not subtract arguments from different sections.
4064 @c FIXME is there still something useful to say about undefined - undefined ?
4066 @cindex comparison expressions
4067 @cindex expressions, comparison
4072 @dfn{Is Not Equal To}
4076 @dfn{Is Greater Than}
4078 @dfn{Is Greater Than Or Equal To}
4080 @dfn{Is Less Than Or Equal To}
4082 The comparison operators can be used as infix operators. A true results has a
4083 value of -1 whereas a false result has a value of 0. Note, these operators
4084 perform signed comparisons.
4087 @item Lowest Precedence
4096 These two logical operations can be used to combine the results of sub
4097 expressions. Note, unlike the comparison operators a true result returns a
4098 value of 1 but a false results does still return 0. Also note that the logical
4099 or operator has a slightly lower precedence than logical and.
4104 In short, it's only meaningful to add or subtract the @emph{offsets} in an
4105 address; you can only have a defined section in one of the two arguments.
4108 @chapter Assembler Directives
4110 @cindex directives, machine independent
4111 @cindex pseudo-ops, machine independent
4112 @cindex machine independent directives
4113 All assembler directives have names that begin with a period (@samp{.}).
4114 The rest of the name is letters, usually in lower case.
4116 This chapter discusses directives that are available regardless of the
4117 target machine configuration for the @sc{gnu} assembler.
4119 Some machine configurations provide additional directives.
4120 @xref{Machine Dependencies}.
4123 @ifset machine-directives
4124 @xref{Machine Dependencies}, for additional directives.
4129 * Abort:: @code{.abort}
4131 * ABORT (COFF):: @code{.ABORT}
4134 * Align:: @code{.align @var{abs-expr} , @var{abs-expr}}
4135 * Altmacro:: @code{.altmacro}
4136 * Ascii:: @code{.ascii "@var{string}"}@dots{}
4137 * Asciz:: @code{.asciz "@var{string}"}@dots{}
4138 * Balign:: @code{.balign @var{abs-expr} , @var{abs-expr}}
4139 * Bundle directives:: @code{.bundle_align_mode @var{abs-expr}}, @code{.bundle_lock}, @code{.bundle_unlock}
4140 * Byte:: @code{.byte @var{expressions}}
4141 * CFI directives:: @code{.cfi_startproc [simple]}, @code{.cfi_endproc}, etc.
4142 * Comm:: @code{.comm @var{symbol} , @var{length} }
4143 * Data:: @code{.data @var{subsection}}
4145 * Def:: @code{.def @var{name}}
4148 * Desc:: @code{.desc @var{symbol}, @var{abs-expression}}
4154 * Double:: @code{.double @var{flonums}}
4155 * Eject:: @code{.eject}
4156 * Else:: @code{.else}
4157 * Elseif:: @code{.elseif}
4160 * Endef:: @code{.endef}
4163 * Endfunc:: @code{.endfunc}
4164 * Endif:: @code{.endif}
4165 * Equ:: @code{.equ @var{symbol}, @var{expression}}
4166 * Equiv:: @code{.equiv @var{symbol}, @var{expression}}
4167 * Eqv:: @code{.eqv @var{symbol}, @var{expression}}
4169 * Error:: @code{.error @var{string}}
4170 * Exitm:: @code{.exitm}
4171 * Extern:: @code{.extern}
4172 * Fail:: @code{.fail}
4173 * File:: @code{.file}
4174 * Fill:: @code{.fill @var{repeat} , @var{size} , @var{value}}
4175 * Float:: @code{.float @var{flonums}}
4176 * Func:: @code{.func}
4177 * Global:: @code{.global @var{symbol}}, @code{.globl @var{symbol}}
4179 * Gnu_attribute:: @code{.gnu_attribute @var{tag},@var{value}}
4180 * Hidden:: @code{.hidden @var{names}}
4183 * hword:: @code{.hword @var{expressions}}
4184 * Ident:: @code{.ident}
4185 * If:: @code{.if @var{absolute expression}}
4186 * Incbin:: @code{.incbin "@var{file}"[,@var{skip}[,@var{count}]]}
4187 * Include:: @code{.include "@var{file}"}
4188 * Int:: @code{.int @var{expressions}}
4190 * Internal:: @code{.internal @var{names}}
4193 * Irp:: @code{.irp @var{symbol},@var{values}}@dots{}
4194 * Irpc:: @code{.irpc @var{symbol},@var{values}}@dots{}
4195 * Lcomm:: @code{.lcomm @var{symbol} , @var{length}}
4196 * Lflags:: @code{.lflags}
4197 @ifclear no-line-dir
4198 * Line:: @code{.line @var{line-number}}
4201 * Linkonce:: @code{.linkonce [@var{type}]}
4202 * List:: @code{.list}
4203 * Ln:: @code{.ln @var{line-number}}
4204 * Loc:: @code{.loc @var{fileno} @var{lineno}}
4205 * Loc_mark_labels:: @code{.loc_mark_labels @var{enable}}
4207 * Local:: @code{.local @var{names}}
4210 * Long:: @code{.long @var{expressions}}
4212 * Lsym:: @code{.lsym @var{symbol}, @var{expression}}
4215 * Macro:: @code{.macro @var{name} @var{args}}@dots{}
4216 * MRI:: @code{.mri @var{val}}
4217 * Noaltmacro:: @code{.noaltmacro}
4218 * Nolist:: @code{.nolist}
4219 * Octa:: @code{.octa @var{bignums}}
4220 * Offset:: @code{.offset @var{loc}}
4221 * Org:: @code{.org @var{new-lc}, @var{fill}}
4222 * P2align:: @code{.p2align @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
4224 * PopSection:: @code{.popsection}
4225 * Previous:: @code{.previous}
4228 * Print:: @code{.print @var{string}}
4230 * Protected:: @code{.protected @var{names}}
4233 * Psize:: @code{.psize @var{lines}, @var{columns}}
4234 * Purgem:: @code{.purgem @var{name}}
4236 * PushSection:: @code{.pushsection @var{name}}
4239 * Quad:: @code{.quad @var{bignums}}
4240 * Reloc:: @code{.reloc @var{offset}, @var{reloc_name}[, @var{expression}]}
4241 * Rept:: @code{.rept @var{count}}
4242 * Sbttl:: @code{.sbttl "@var{subheading}"}
4244 * Scl:: @code{.scl @var{class}}
4247 * Section:: @code{.section @var{name}[, @var{flags}]}
4250 * Set:: @code{.set @var{symbol}, @var{expression}}
4251 * Short:: @code{.short @var{expressions}}
4252 * Single:: @code{.single @var{flonums}}
4254 * Size:: @code{.size [@var{name} , @var{expression}]}
4256 @ifclear no-space-dir
4257 * Skip:: @code{.skip @var{size} , @var{fill}}
4260 * Sleb128:: @code{.sleb128 @var{expressions}}
4261 @ifclear no-space-dir
4262 * Space:: @code{.space @var{size} , @var{fill}}
4265 * Stab:: @code{.stabd, .stabn, .stabs}
4268 * String:: @code{.string "@var{str}"}, @code{.string8 "@var{str}"}, @code{.string16 "@var{str}"}, @code{.string32 "@var{str}"}, @code{.string64 "@var{str}"}
4269 * Struct:: @code{.struct @var{expression}}
4271 * SubSection:: @code{.subsection}
4272 * Symver:: @code{.symver @var{name},@var{name2@@nodename}}
4276 * Tag:: @code{.tag @var{structname}}
4279 * Text:: @code{.text @var{subsection}}
4280 * Title:: @code{.title "@var{heading}"}
4282 * Type:: @code{.type <@var{int} | @var{name} , @var{type description}>}
4285 * Uleb128:: @code{.uleb128 @var{expressions}}
4287 * Val:: @code{.val @var{addr}}
4291 * Version:: @code{.version "@var{string}"}
4292 * VTableEntry:: @code{.vtable_entry @var{table}, @var{offset}}
4293 * VTableInherit:: @code{.vtable_inherit @var{child}, @var{parent}}
4296 * Warning:: @code{.warning @var{string}}
4297 * Weak:: @code{.weak @var{names}}
4298 * Weakref:: @code{.weakref @var{alias}, @var{symbol}}
4299 * Word:: @code{.word @var{expressions}}
4300 * Deprecated:: Deprecated Directives
4304 @section @code{.abort}
4306 @cindex @code{abort} directive
4307 @cindex stopping the assembly
4308 This directive stops the assembly immediately. It is for
4309 compatibility with other assemblers. The original idea was that the
4310 assembly language source would be piped into the assembler. If the sender
4311 of the source quit, it could use this directive tells @command{@value{AS}} to
4312 quit also. One day @code{.abort} will not be supported.
4316 @section @code{.ABORT} (COFF)
4318 @cindex @code{ABORT} directive
4319 When producing COFF output, @command{@value{AS}} accepts this directive as a
4320 synonym for @samp{.abort}.
4323 When producing @code{b.out} output, @command{@value{AS}} accepts this directive,
4329 @section @code{.align @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
4331 @cindex padding the location counter
4332 @cindex @code{align} directive
4333 Pad the location counter (in the current subsection) to a particular storage
4334 boundary. The first expression (which must be absolute) is the alignment
4335 required, as described below.
4337 The second expression (also absolute) gives the fill value to be stored in the
4338 padding bytes. It (and the comma) may be omitted. If it is omitted, the
4339 padding bytes are normally zero. However, on some systems, if the section is
4340 marked as containing code and the fill value is omitted, the space is filled
4341 with no-op instructions.
4343 The third expression is also absolute, and is also optional. If it is present,
4344 it is the maximum number of bytes that should be skipped by this alignment
4345 directive. If doing the alignment would require skipping more bytes than the
4346 specified maximum, then the alignment is not done at all. You can omit the
4347 fill value (the second argument) entirely by simply using two commas after the
4348 required alignment; this can be useful if you want the alignment to be filled
4349 with no-op instructions when appropriate.
4351 The way the required alignment is specified varies from system to system.
4352 For the arc, hppa, i386 using ELF, i860, iq2000, m68k, or32,
4353 s390, sparc, tic4x, tic80 and xtensa, the first expression is the
4354 alignment request in bytes. For example @samp{.align 8} advances
4355 the location counter until it is a multiple of 8. If the location counter
4356 is already a multiple of 8, no change is needed. For the tic54x, the
4357 first expression is the alignment request in words.
4359 For other systems, including ppc, i386 using a.out format, arm and
4360 strongarm, it is the
4361 number of low-order zero bits the location counter must have after
4362 advancement. For example @samp{.align 3} advances the location
4363 counter until it a multiple of 8. If the location counter is already a
4364 multiple of 8, no change is needed.
4366 This inconsistency is due to the different behaviors of the various
4367 native assemblers for these systems which GAS must emulate.
4368 GAS also provides @code{.balign} and @code{.p2align} directives,
4369 described later, which have a consistent behavior across all
4370 architectures (but are specific to GAS).
4373 @section @code{.altmacro}
4374 Enable alternate macro mode, enabling:
4377 @item LOCAL @var{name} [ , @dots{} ]
4378 One additional directive, @code{LOCAL}, is available. It is used to
4379 generate a string replacement for each of the @var{name} arguments, and
4380 replace any instances of @var{name} in each macro expansion. The
4381 replacement string is unique in the assembly, and different for each
4382 separate macro expansion. @code{LOCAL} allows you to write macros that
4383 define symbols, without fear of conflict between separate macro expansions.
4385 @item String delimiters
4386 You can write strings delimited in these other ways besides
4387 @code{"@var{string}"}:
4390 @item '@var{string}'
4391 You can delimit strings with single-quote characters.
4393 @item <@var{string}>
4394 You can delimit strings with matching angle brackets.
4397 @item single-character string escape
4398 To include any single character literally in a string (even if the
4399 character would otherwise have some special meaning), you can prefix the
4400 character with @samp{!} (an exclamation mark). For example, you can
4401 write @samp{<4.3 !> 5.4!!>} to get the literal text @samp{4.3 > 5.4!}.
4403 @item Expression results as strings
4404 You can write @samp{%@var{expr}} to evaluate the expression @var{expr}
4405 and use the result as a string.
4409 @section @code{.ascii "@var{string}"}@dots{}
4411 @cindex @code{ascii} directive
4412 @cindex string literals
4413 @code{.ascii} expects zero or more string literals (@pxref{Strings})
4414 separated by commas. It assembles each string (with no automatic
4415 trailing zero byte) into consecutive addresses.
4418 @section @code{.asciz "@var{string}"}@dots{}
4420 @cindex @code{asciz} directive
4421 @cindex zero-terminated strings
4422 @cindex null-terminated strings
4423 @code{.asciz} is just like @code{.ascii}, but each string is followed by
4424 a zero byte. The ``z'' in @samp{.asciz} stands for ``zero''.
4427 @section @code{.balign[wl] @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
4429 @cindex padding the location counter given number of bytes
4430 @cindex @code{balign} directive
4431 Pad the location counter (in the current subsection) to a particular
4432 storage boundary. The first expression (which must be absolute) is the
4433 alignment request in bytes. For example @samp{.balign 8} advances
4434 the location counter until it is a multiple of 8. If the location counter
4435 is already a multiple of 8, no change is needed.
4437 The second expression (also absolute) gives the fill value to be stored in the
4438 padding bytes. It (and the comma) may be omitted. If it is omitted, the
4439 padding bytes are normally zero. However, on some systems, if the section is
4440 marked as containing code and the fill value is omitted, the space is filled
4441 with no-op instructions.
4443 The third expression is also absolute, and is also optional. If it is present,
4444 it is the maximum number of bytes that should be skipped by this alignment
4445 directive. If doing the alignment would require skipping more bytes than the
4446 specified maximum, then the alignment is not done at all. You can omit the
4447 fill value (the second argument) entirely by simply using two commas after the
4448 required alignment; this can be useful if you want the alignment to be filled
4449 with no-op instructions when appropriate.
4451 @cindex @code{balignw} directive
4452 @cindex @code{balignl} directive
4453 The @code{.balignw} and @code{.balignl} directives are variants of the
4454 @code{.balign} directive. The @code{.balignw} directive treats the fill
4455 pattern as a two byte word value. The @code{.balignl} directives treats the
4456 fill pattern as a four byte longword value. For example, @code{.balignw
4457 4,0x368d} will align to a multiple of 4. If it skips two bytes, they will be
4458 filled in with the value 0x368d (the exact placement of the bytes depends upon
4459 the endianness of the processor). If it skips 1 or 3 bytes, the fill value is
4462 @node Bundle directives
4463 @section @code{.bundle_align_mode @var{abs-expr}}
4464 @cindex @code{bundle_align_mode} directive
4466 @cindex instruction bundle
4467 @cindex aligned instruction bundle
4468 @code{.bundle_align_mode} enables or disables @dfn{aligned instruction
4469 bundle} mode. In this mode, sequences of adjacent instructions are grouped
4470 into fixed-sized @dfn{bundles}. If the argument is zero, this mode is
4471 disabled (which is the default state). If the argument it not zero, it
4472 gives the size of an instruction bundle as a power of two (as for the
4473 @code{.p2align} directive, @pxref{P2align}).
4475 For some targets, it's an ABI requirement that no instruction may span a
4476 certain aligned boundary. A @dfn{bundle} is simply a sequence of
4477 instructions that starts on an aligned boundary. For example, if
4478 @var{abs-expr} is @code{5} then the bundle size is 32, so each aligned
4479 chunk of 32 bytes is a bundle. When aligned instruction bundle mode is in
4480 effect, no single instruction may span a boundary between bundles. If an
4481 instruction would start too close to the end of a bundle for the length of
4482 that particular instruction to fit within the bundle, then the space at the
4483 end of that bundle is filled with no-op instructions so the instruction
4484 starts in the next bundle. As a corollary, it's an error if any single
4485 instruction's encoding is longer than the bundle size.
4487 @section @code{.bundle_lock} and @code{.bundle_unlock}
4488 @cindex @code{bundle_lock} directive
4489 @cindex @code{bundle_unlock} directive
4490 The @code{.bundle_lock} and directive @code{.bundle_unlock} directives
4491 allow explicit control over instruction bundle padding. These directives
4492 are only valid when @code{.bundle_align_mode} has been used to enable
4493 aligned instruction bundle mode. It's an error if they appear when
4494 @code{.bundle_align_mode} has not been used at all, or when the last
4495 directive was @w{@code{.bundle_align_mode 0}}.
4497 @cindex bundle-locked
4498 For some targets, it's an ABI requirement that certain instructions may
4499 appear only as part of specified permissible sequences of multiple
4500 instructions, all within the same bundle. A pair of @code{.bundle_lock}
4501 and @code{.bundle_unlock} directives define a @dfn{bundle-locked}
4502 instruction sequence. For purposes of aligned instruction bundle mode, a
4503 sequence starting with @code{.bundle_lock} and ending with
4504 @code{.bundle_unlock} is treated as a single instruction. That is, the
4505 entire sequence must fit into a single bundle and may not span a bundle
4506 boundary. If necessary, no-op instructions will be inserted before the
4507 first instruction of the sequence so that the whole sequence starts on an
4508 aligned bundle boundary. It's an error if the sequence is longer than the
4511 For convenience when using @code{.bundle_lock} and @code{.bundle_unlock}
4512 inside assembler macros (@pxref{Macro}), bundle-locked sequences may be
4513 nested. That is, a second @code{.bundle_lock} directive before the next
4514 @code{.bundle_unlock} directive has no effect except that it must be
4515 matched by another closing @code{.bundle_unlock} so that there is the
4516 same number of @code{.bundle_lock} and @code{.bundle_unlock} directives.
4519 @section @code{.byte @var{expressions}}
4521 @cindex @code{byte} directive
4522 @cindex integers, one byte
4523 @code{.byte} expects zero or more expressions, separated by commas.
4524 Each expression is assembled into the next byte.
4526 @node CFI directives
4527 @section @code{.cfi_sections @var{section_list}}
4528 @cindex @code{cfi_sections} directive
4529 @code{.cfi_sections} may be used to specify whether CFI directives
4530 should emit @code{.eh_frame} section and/or @code{.debug_frame} section.
4531 If @var{section_list} is @code{.eh_frame}, @code{.eh_frame} is emitted,
4532 if @var{section_list} is @code{.debug_frame}, @code{.debug_frame} is emitted.
4533 To emit both use @code{.eh_frame, .debug_frame}. The default if this
4534 directive is not used is @code{.cfi_sections .eh_frame}.
4536 @section @code{.cfi_startproc [simple]}
4537 @cindex @code{cfi_startproc} directive
4538 @code{.cfi_startproc} is used at the beginning of each function that
4539 should have an entry in @code{.eh_frame}. It initializes some internal
4540 data structures. Don't forget to close the function by
4541 @code{.cfi_endproc}.
4543 Unless @code{.cfi_startproc} is used along with parameter @code{simple}
4544 it also emits some architecture dependent initial CFI instructions.
4546 @section @code{.cfi_endproc}
4547 @cindex @code{cfi_endproc} directive
4548 @code{.cfi_endproc} is used at the end of a function where it closes its
4549 unwind entry previously opened by
4550 @code{.cfi_startproc}, and emits it to @code{.eh_frame}.
4552 @section @code{.cfi_personality @var{encoding} [, @var{exp}]}
4553 @code{.cfi_personality} defines personality routine and its encoding.
4554 @var{encoding} must be a constant determining how the personality
4555 should be encoded. If it is 255 (@code{DW_EH_PE_omit}), second
4556 argument is not present, otherwise second argument should be
4557 a constant or a symbol name. When using indirect encodings,
4558 the symbol provided should be the location where personality
4559 can be loaded from, not the personality routine itself.
4560 The default after @code{.cfi_startproc} is @code{.cfi_personality 0xff},
4561 no personality routine.
4563 @section @code{.cfi_lsda @var{encoding} [, @var{exp}]}
4564 @code{.cfi_lsda} defines LSDA and its encoding.
4565 @var{encoding} must be a constant determining how the LSDA
4566 should be encoded. If it is 255 (@code{DW_EH_PE_omit}), second
4567 argument is not present, otherwise second argument should be a constant
4568 or a symbol name. The default after @code{.cfi_startproc} is @code{.cfi_lsda 0xff},
4571 @section @code{.cfi_def_cfa @var{register}, @var{offset}}
4572 @code{.cfi_def_cfa} defines a rule for computing CFA as: @i{take
4573 address from @var{register} and add @var{offset} to it}.
4575 @section @code{.cfi_def_cfa_register @var{register}}
4576 @code{.cfi_def_cfa_register} modifies a rule for computing CFA. From
4577 now on @var{register} will be used instead of the old one. Offset
4580 @section @code{.cfi_def_cfa_offset @var{offset}}
4581 @code{.cfi_def_cfa_offset} modifies a rule for computing CFA. Register
4582 remains the same, but @var{offset} is new. Note that it is the
4583 absolute offset that will be added to a defined register to compute
4586 @section @code{.cfi_adjust_cfa_offset @var{offset}}
4587 Same as @code{.cfi_def_cfa_offset} but @var{offset} is a relative
4588 value that is added/substracted from the previous offset.
4590 @section @code{.cfi_offset @var{register}, @var{offset}}
4591 Previous value of @var{register} is saved at offset @var{offset} from
4594 @section @code{.cfi_rel_offset @var{register}, @var{offset}}
4595 Previous value of @var{register} is saved at offset @var{offset} from
4596 the current CFA register. This is transformed to @code{.cfi_offset}
4597 using the known displacement of the CFA register from the CFA.
4598 This is often easier to use, because the number will match the
4599 code it's annotating.
4601 @section @code{.cfi_register @var{register1}, @var{register2}}
4602 Previous value of @var{register1} is saved in register @var{register2}.
4604 @section @code{.cfi_restore @var{register}}
4605 @code{.cfi_restore} says that the rule for @var{register} is now the
4606 same as it was at the beginning of the function, after all initial
4607 instruction added by @code{.cfi_startproc} were executed.
4609 @section @code{.cfi_undefined @var{register}}
4610 From now on the previous value of @var{register} can't be restored anymore.
4612 @section @code{.cfi_same_value @var{register}}
4613 Current value of @var{register} is the same like in the previous frame,
4614 i.e. no restoration needed.
4616 @section @code{.cfi_remember_state},
4617 First save all current rules for all registers by @code{.cfi_remember_state},
4618 then totally screw them up by subsequent @code{.cfi_*} directives and when
4619 everything is hopelessly bad, use @code{.cfi_restore_state} to restore
4620 the previous saved state.
4622 @section @code{.cfi_return_column @var{register}}
4623 Change return column @var{register}, i.e. the return address is either
4624 directly in @var{register} or can be accessed by rules for @var{register}.
4626 @section @code{.cfi_signal_frame}
4627 Mark current function as signal trampoline.
4629 @section @code{.cfi_window_save}
4630 SPARC register window has been saved.
4632 @section @code{.cfi_escape} @var{expression}[, @dots{}]
4633 Allows the user to add arbitrary bytes to the unwind info. One
4634 might use this to add OS-specific CFI opcodes, or generic CFI
4635 opcodes that GAS does not yet support.
4637 @section @code{.cfi_val_encoded_addr @var{register}, @var{encoding}, @var{label}}
4638 The current value of @var{register} is @var{label}. The value of @var{label}
4639 will be encoded in the output file according to @var{encoding}; see the
4640 description of @code{.cfi_personality} for details on this encoding.
4642 The usefulness of equating a register to a fixed label is probably
4643 limited to the return address register. Here, it can be useful to
4644 mark a code segment that has only one return address which is reached
4645 by a direct branch and no copy of the return address exists in memory
4646 or another register.
4649 @section @code{.comm @var{symbol} , @var{length} }
4651 @cindex @code{comm} directive
4652 @cindex symbol, common
4653 @code{.comm} declares a common symbol named @var{symbol}. When linking, a
4654 common symbol in one object file may be merged with a defined or common symbol
4655 of the same name in another object file. If @code{@value{LD}} does not see a
4656 definition for the symbol--just one or more common symbols--then it will
4657 allocate @var{length} bytes of uninitialized memory. @var{length} must be an
4658 absolute expression. If @code{@value{LD}} sees multiple common symbols with
4659 the same name, and they do not all have the same size, it will allocate space
4660 using the largest size.
4663 When using ELF or (as a GNU extension) PE, the @code{.comm} directive takes
4664 an optional third argument. This is the desired alignment of the symbol,
4665 specified for ELF as a byte boundary (for example, an alignment of 16 means
4666 that the least significant 4 bits of the address should be zero), and for PE
4667 as a power of two (for example, an alignment of 5 means aligned to a 32-byte
4668 boundary). The alignment must be an absolute expression, and it must be a
4669 power of two. If @code{@value{LD}} allocates uninitialized memory for the
4670 common symbol, it will use the alignment when placing the symbol. If no
4671 alignment is specified, @command{@value{AS}} will set the alignment to the
4672 largest power of two less than or equal to the size of the symbol, up to a
4673 maximum of 16 on ELF, or the default section alignment of 4 on PE@footnote{This
4674 is not the same as the executable image file alignment controlled by @code{@value{LD}}'s
4675 @samp{--section-alignment} option; image file sections in PE are aligned to
4676 multiples of 4096, which is far too large an alignment for ordinary variables.
4677 It is rather the default alignment for (non-debug) sections within object
4678 (@samp{*.o}) files, which are less strictly aligned.}.
4682 The syntax for @code{.comm} differs slightly on the HPPA. The syntax is
4683 @samp{@var{symbol} .comm, @var{length}}; @var{symbol} is optional.
4687 @section @code{.data @var{subsection}}
4689 @cindex @code{data} directive
4690 @code{.data} tells @command{@value{AS}} to assemble the following statements onto the
4691 end of the data subsection numbered @var{subsection} (which is an
4692 absolute expression). If @var{subsection} is omitted, it defaults
4697 @section @code{.def @var{name}}
4699 @cindex @code{def} directive
4700 @cindex COFF symbols, debugging
4701 @cindex debugging COFF symbols
4702 Begin defining debugging information for a symbol @var{name}; the
4703 definition extends until the @code{.endef} directive is encountered.
4706 This directive is only observed when @command{@value{AS}} is configured for COFF
4707 format output; when producing @code{b.out}, @samp{.def} is recognized,
4714 @section @code{.desc @var{symbol}, @var{abs-expression}}
4716 @cindex @code{desc} directive
4717 @cindex COFF symbol descriptor
4718 @cindex symbol descriptor, COFF
4719 This directive sets the descriptor of the symbol (@pxref{Symbol Attributes})
4720 to the low 16 bits of an absolute expression.
4723 The @samp{.desc} directive is not available when @command{@value{AS}} is
4724 configured for COFF output; it is only for @code{a.out} or @code{b.out}
4725 object format. For the sake of compatibility, @command{@value{AS}} accepts
4726 it, but produces no output, when configured for COFF.
4732 @section @code{.dim}
4734 @cindex @code{dim} directive
4735 @cindex COFF auxiliary symbol information
4736 @cindex auxiliary symbol information, COFF
4737 This directive is generated by compilers to include auxiliary debugging
4738 information in the symbol table. It is only permitted inside
4739 @code{.def}/@code{.endef} pairs.
4742 @samp{.dim} is only meaningful when generating COFF format output; when
4743 @command{@value{AS}} is generating @code{b.out}, it accepts this directive but
4749 @section @code{.double @var{flonums}}
4751 @cindex @code{double} directive
4752 @cindex floating point numbers (double)
4753 @code{.double} expects zero or more flonums, separated by commas. It
4754 assembles floating point numbers.
4756 The exact kind of floating point numbers emitted depends on how
4757 @command{@value{AS}} is configured. @xref{Machine Dependencies}.
4761 On the @value{TARGET} family @samp{.double} emits 64-bit floating-point numbers
4762 in @sc{ieee} format.
4767 @section @code{.eject}
4769 @cindex @code{eject} directive
4770 @cindex new page, in listings
4771 @cindex page, in listings
4772 @cindex listing control: new page
4773 Force a page break at this point, when generating assembly listings.
4776 @section @code{.else}
4778 @cindex @code{else} directive
4779 @code{.else} is part of the @command{@value{AS}} support for conditional
4780 assembly; see @ref{If,,@code{.if}}. It marks the beginning of a section
4781 of code to be assembled if the condition for the preceding @code{.if}
4785 @section @code{.elseif}
4787 @cindex @code{elseif} directive
4788 @code{.elseif} is part of the @command{@value{AS}} support for conditional
4789 assembly; see @ref{If,,@code{.if}}. It is shorthand for beginning a new
4790 @code{.if} block that would otherwise fill the entire @code{.else} section.
4793 @section @code{.end}
4795 @cindex @code{end} directive
4796 @code{.end} marks the end of the assembly file. @command{@value{AS}} does not
4797 process anything in the file past the @code{.end} directive.
4801 @section @code{.endef}
4803 @cindex @code{endef} directive
4804 This directive flags the end of a symbol definition begun with
4808 @samp{.endef} is only meaningful when generating COFF format output; if
4809 @command{@value{AS}} is configured to generate @code{b.out}, it accepts this
4810 directive but ignores it.
4815 @section @code{.endfunc}
4816 @cindex @code{endfunc} directive
4817 @code{.endfunc} marks the end of a function specified with @code{.func}.
4820 @section @code{.endif}
4822 @cindex @code{endif} directive
4823 @code{.endif} is part of the @command{@value{AS}} support for conditional assembly;
4824 it marks the end of a block of code that is only assembled
4825 conditionally. @xref{If,,@code{.if}}.
4828 @section @code{.equ @var{symbol}, @var{expression}}
4830 @cindex @code{equ} directive
4831 @cindex assigning values to symbols
4832 @cindex symbols, assigning values to
4833 This directive sets the value of @var{symbol} to @var{expression}.
4834 It is synonymous with @samp{.set}; see @ref{Set,,@code{.set}}.
4837 The syntax for @code{equ} on the HPPA is
4838 @samp{@var{symbol} .equ @var{expression}}.
4842 The syntax for @code{equ} on the Z80 is
4843 @samp{@var{symbol} equ @var{expression}}.
4844 On the Z80 it is an eror if @var{symbol} is already defined,
4845 but the symbol is not protected from later redefinition.
4846 Compare @ref{Equiv}.
4850 @section @code{.equiv @var{symbol}, @var{expression}}
4851 @cindex @code{equiv} directive
4852 The @code{.equiv} directive is like @code{.equ} and @code{.set}, except that
4853 the assembler will signal an error if @var{symbol} is already defined. Note a
4854 symbol which has been referenced but not actually defined is considered to be
4857 Except for the contents of the error message, this is roughly equivalent to
4864 plus it protects the symbol from later redefinition.
4867 @section @code{.eqv @var{symbol}, @var{expression}}
4868 @cindex @code{eqv} directive
4869 The @code{.eqv} directive is like @code{.equiv}, but no attempt is made to
4870 evaluate the expression or any part of it immediately. Instead each time
4871 the resulting symbol is used in an expression, a snapshot of its current
4875 @section @code{.err}
4876 @cindex @code{err} directive
4877 If @command{@value{AS}} assembles a @code{.err} directive, it will print an error
4878 message and, unless the @option{-Z} option was used, it will not generate an
4879 object file. This can be used to signal an error in conditionally compiled code.
4882 @section @code{.error "@var{string}"}
4883 @cindex error directive
4885 Similarly to @code{.err}, this directive emits an error, but you can specify a
4886 string that will be emitted as the error message. If you don't specify the
4887 message, it defaults to @code{".error directive invoked in source file"}.
4888 @xref{Errors, ,Error and Warning Messages}.
4891 .error "This code has not been assembled and tested."
4895 @section @code{.exitm}
4896 Exit early from the current macro definition. @xref{Macro}.
4899 @section @code{.extern}
4901 @cindex @code{extern} directive
4902 @code{.extern} is accepted in the source program---for compatibility
4903 with other assemblers---but it is ignored. @command{@value{AS}} treats
4904 all undefined symbols as external.
4907 @section @code{.fail @var{expression}}
4909 @cindex @code{fail} directive
4910 Generates an error or a warning. If the value of the @var{expression} is 500
4911 or more, @command{@value{AS}} will print a warning message. If the value is less
4912 than 500, @command{@value{AS}} will print an error message. The message will
4913 include the value of @var{expression}. This can occasionally be useful inside
4914 complex nested macros or conditional assembly.
4917 @section @code{.file}
4918 @cindex @code{file} directive
4920 @ifclear no-file-dir
4921 There are two different versions of the @code{.file} directive. Targets
4922 that support DWARF2 line number information use the DWARF2 version of
4923 @code{.file}. Other targets use the default version.
4925 @subheading Default Version
4927 @cindex logical file name
4928 @cindex file name, logical
4929 This version of the @code{.file} directive tells @command{@value{AS}} that we
4930 are about to start a new logical file. The syntax is:
4936 @var{string} is the new file name. In general, the filename is
4937 recognized whether or not it is surrounded by quotes @samp{"}; but if you wish
4938 to specify an empty file name, you must give the quotes--@code{""}. This
4939 statement may go away in future: it is only recognized to be compatible with
4940 old @command{@value{AS}} programs.
4942 @subheading DWARF2 Version
4945 When emitting DWARF2 line number information, @code{.file} assigns filenames
4946 to the @code{.debug_line} file name table. The syntax is:
4949 .file @var{fileno} @var{filename}
4952 The @var{fileno} operand should be a unique positive integer to use as the
4953 index of the entry in the table. The @var{filename} operand is a C string
4956 The detail of filename indices is exposed to the user because the filename
4957 table is shared with the @code{.debug_info} section of the DWARF2 debugging
4958 information, and thus the user must know the exact indices that table
4962 @section @code{.fill @var{repeat} , @var{size} , @var{value}}
4964 @cindex @code{fill} directive
4965 @cindex writing patterns in memory
4966 @cindex patterns, writing in memory
4967 @var{repeat}, @var{size} and @var{value} are absolute expressions.
4968 This emits @var{repeat} copies of @var{size} bytes. @var{Repeat}
4969 may be zero or more. @var{Size} may be zero or more, but if it is
4970 more than 8, then it is deemed to have the value 8, compatible with
4971 other people's assemblers. The contents of each @var{repeat} bytes
4972 is taken from an 8-byte number. The highest order 4 bytes are
4973 zero. The lowest order 4 bytes are @var{value} rendered in the
4974 byte-order of an integer on the computer @command{@value{AS}} is assembling for.
4975 Each @var{size} bytes in a repetition is taken from the lowest order
4976 @var{size} bytes of this number. Again, this bizarre behavior is
4977 compatible with other people's assemblers.
4979 @var{size} and @var{value} are optional.
4980 If the second comma and @var{value} are absent, @var{value} is
4981 assumed zero. If the first comma and following tokens are absent,
4982 @var{size} is assumed to be 1.
4985 @section @code{.float @var{flonums}}
4987 @cindex floating point numbers (single)
4988 @cindex @code{float} directive
4989 This directive assembles zero or more flonums, separated by commas. It
4990 has the same effect as @code{.single}.
4992 The exact kind of floating point numbers emitted depends on how
4993 @command{@value{AS}} is configured.
4994 @xref{Machine Dependencies}.
4998 On the @value{TARGET} family, @code{.float} emits 32-bit floating point numbers
4999 in @sc{ieee} format.
5004 @section @code{.func @var{name}[,@var{label}]}
5005 @cindex @code{func} directive
5006 @code{.func} emits debugging information to denote function @var{name}, and
5007 is ignored unless the file is assembled with debugging enabled.
5008 Only @samp{--gstabs[+]} is currently supported.
5009 @var{label} is the entry point of the function and if omitted @var{name}
5010 prepended with the @samp{leading char} is used.
5011 @samp{leading char} is usually @code{_} or nothing, depending on the target.
5012 All functions are currently defined to have @code{void} return type.
5013 The function must be terminated with @code{.endfunc}.
5016 @section @code{.global @var{symbol}}, @code{.globl @var{symbol}}
5018 @cindex @code{global} directive
5019 @cindex symbol, making visible to linker
5020 @code{.global} makes the symbol visible to @code{@value{LD}}. If you define
5021 @var{symbol} in your partial program, its value is made available to
5022 other partial programs that are linked with it. Otherwise,
5023 @var{symbol} takes its attributes from a symbol of the same name
5024 from another file linked into the same program.
5026 Both spellings (@samp{.globl} and @samp{.global}) are accepted, for
5027 compatibility with other assemblers.
5030 On the HPPA, @code{.global} is not always enough to make it accessible to other
5031 partial programs. You may need the HPPA-only @code{.EXPORT} directive as well.
5032 @xref{HPPA Directives, ,HPPA Assembler Directives}.
5037 @section @code{.gnu_attribute @var{tag},@var{value}}
5038 Record a @sc{gnu} object attribute for this file. @xref{Object Attributes}.
5041 @section @code{.hidden @var{names}}
5043 @cindex @code{hidden} directive
5045 This is one of the ELF visibility directives. The other two are
5046 @code{.internal} (@pxref{Internal,,@code{.internal}}) and
5047 @code{.protected} (@pxref{Protected,,@code{.protected}}).
5049 This directive overrides the named symbols default visibility (which is set by
5050 their binding: local, global or weak). The directive sets the visibility to
5051 @code{hidden} which means that the symbols are not visible to other components.
5052 Such symbols are always considered to be @code{protected} as well.
5056 @section @code{.hword @var{expressions}}
5058 @cindex @code{hword} directive
5059 @cindex integers, 16-bit
5060 @cindex numbers, 16-bit
5061 @cindex sixteen bit integers
5062 This expects zero or more @var{expressions}, and emits
5063 a 16 bit number for each.
5066 This directive is a synonym for @samp{.short}; depending on the target
5067 architecture, it may also be a synonym for @samp{.word}.
5071 This directive is a synonym for @samp{.short}.
5074 This directive is a synonym for both @samp{.short} and @samp{.word}.
5079 @section @code{.ident}
5081 @cindex @code{ident} directive
5083 This directive is used by some assemblers to place tags in object files. The
5084 behavior of this directive varies depending on the target. When using the
5085 a.out object file format, @command{@value{AS}} simply accepts the directive for
5086 source-file compatibility with existing assemblers, but does not emit anything
5087 for it. When using COFF, comments are emitted to the @code{.comment} or
5088 @code{.rdata} section, depending on the target. When using ELF, comments are
5089 emitted to the @code{.comment} section.
5092 @section @code{.if @var{absolute expression}}
5094 @cindex conditional assembly
5095 @cindex @code{if} directive
5096 @code{.if} marks the beginning of a section of code which is only
5097 considered part of the source program being assembled if the argument
5098 (which must be an @var{absolute expression}) is non-zero. The end of
5099 the conditional section of code must be marked by @code{.endif}
5100 (@pxref{Endif,,@code{.endif}}); optionally, you may include code for the
5101 alternative condition, flagged by @code{.else} (@pxref{Else,,@code{.else}}).
5102 If you have several conditions to check, @code{.elseif} may be used to avoid
5103 nesting blocks if/else within each subsequent @code{.else} block.
5105 The following variants of @code{.if} are also supported:
5107 @cindex @code{ifdef} directive
5108 @item .ifdef @var{symbol}
5109 Assembles the following section of code if the specified @var{symbol}
5110 has been defined. Note a symbol which has been referenced but not yet defined
5111 is considered to be undefined.
5113 @cindex @code{ifb} directive
5114 @item .ifb @var{text}
5115 Assembles the following section of code if the operand is blank (empty).
5117 @cindex @code{ifc} directive
5118 @item .ifc @var{string1},@var{string2}
5119 Assembles the following section of code if the two strings are the same. The
5120 strings may be optionally quoted with single quotes. If they are not quoted,
5121 the first string stops at the first comma, and the second string stops at the
5122 end of the line. Strings which contain whitespace should be quoted. The
5123 string comparison is case sensitive.
5125 @cindex @code{ifeq} directive
5126 @item .ifeq @var{absolute expression}
5127 Assembles the following section of code if the argument is zero.
5129 @cindex @code{ifeqs} directive
5130 @item .ifeqs @var{string1},@var{string2}
5131 Another form of @code{.ifc}. The strings must be quoted using double quotes.
5133 @cindex @code{ifge} directive
5134 @item .ifge @var{absolute expression}
5135 Assembles the following section of code if the argument is greater than or
5138 @cindex @code{ifgt} directive
5139 @item .ifgt @var{absolute expression}
5140 Assembles the following section of code if the argument is greater than zero.
5142 @cindex @code{ifle} directive
5143 @item .ifle @var{absolute expression}
5144 Assembles the following section of code if the argument is less than or equal
5147 @cindex @code{iflt} directive
5148 @item .iflt @var{absolute expression}
5149 Assembles the following section of code if the argument is less than zero.
5151 @cindex @code{ifnb} directive
5152 @item .ifnb @var{text}
5153 Like @code{.ifb}, but the sense of the test is reversed: this assembles the
5154 following section of code if the operand is non-blank (non-empty).
5156 @cindex @code{ifnc} directive
5157 @item .ifnc @var{string1},@var{string2}.
5158 Like @code{.ifc}, but the sense of the test is reversed: this assembles the
5159 following section of code if the two strings are not the same.
5161 @cindex @code{ifndef} directive
5162 @cindex @code{ifnotdef} directive
5163 @item .ifndef @var{symbol}
5164 @itemx .ifnotdef @var{symbol}
5165 Assembles the following section of code if the specified @var{symbol}
5166 has not been defined. Both spelling variants are equivalent. Note a symbol
5167 which has been referenced but not yet defined is considered to be undefined.
5169 @cindex @code{ifne} directive
5170 @item .ifne @var{absolute expression}
5171 Assembles the following section of code if the argument is not equal to zero
5172 (in other words, this is equivalent to @code{.if}).
5174 @cindex @code{ifnes} directive
5175 @item .ifnes @var{string1},@var{string2}
5176 Like @code{.ifeqs}, but the sense of the test is reversed: this assembles the
5177 following section of code if the two strings are not the same.
5181 @section @code{.incbin "@var{file}"[,@var{skip}[,@var{count}]]}
5183 @cindex @code{incbin} directive
5184 @cindex binary files, including
5185 The @code{incbin} directive includes @var{file} verbatim at the current
5186 location. You can control the search paths used with the @samp{-I} command-line
5187 option (@pxref{Invoking,,Command-Line Options}). Quotation marks are required
5190 The @var{skip} argument skips a number of bytes from the start of the
5191 @var{file}. The @var{count} argument indicates the maximum number of bytes to
5192 read. Note that the data is not aligned in any way, so it is the user's
5193 responsibility to make sure that proper alignment is provided both before and
5194 after the @code{incbin} directive.
5197 @section @code{.include "@var{file}"}
5199 @cindex @code{include} directive
5200 @cindex supporting files, including
5201 @cindex files, including
5202 This directive provides a way to include supporting files at specified
5203 points in your source program. The code from @var{file} is assembled as
5204 if it followed the point of the @code{.include}; when the end of the
5205 included file is reached, assembly of the original file continues. You
5206 can control the search paths used with the @samp{-I} command-line option
5207 (@pxref{Invoking,,Command-Line Options}). Quotation marks are required
5211 @section @code{.int @var{expressions}}
5213 @cindex @code{int} directive
5214 @cindex integers, 32-bit
5215 Expect zero or more @var{expressions}, of any section, separated by commas.
5216 For each expression, emit a number that, at run time, is the value of that
5217 expression. The byte order and bit size of the number depends on what kind
5218 of target the assembly is for.
5222 On most forms of the H8/300, @code{.int} emits 16-bit
5223 integers. On the H8/300H and the Renesas SH, however, @code{.int} emits
5230 @section @code{.internal @var{names}}
5232 @cindex @code{internal} directive
5234 This is one of the ELF visibility directives. The other two are
5235 @code{.hidden} (@pxref{Hidden,,@code{.hidden}}) and
5236 @code{.protected} (@pxref{Protected,,@code{.protected}}).
5238 This directive overrides the named symbols default visibility (which is set by
5239 their binding: local, global or weak). The directive sets the visibility to
5240 @code{internal} which means that the symbols are considered to be @code{hidden}
5241 (i.e., not visible to other components), and that some extra, processor specific
5242 processing must also be performed upon the symbols as well.
5246 @section @code{.irp @var{symbol},@var{values}}@dots{}
5248 @cindex @code{irp} directive
5249 Evaluate a sequence of statements assigning different values to @var{symbol}.
5250 The sequence of statements starts at the @code{.irp} directive, and is
5251 terminated by an @code{.endr} directive. For each @var{value}, @var{symbol} is
5252 set to @var{value}, and the sequence of statements is assembled. If no
5253 @var{value} is listed, the sequence of statements is assembled once, with
5254 @var{symbol} set to the null string. To refer to @var{symbol} within the
5255 sequence of statements, use @var{\symbol}.
5257 For example, assembling
5265 is equivalent to assembling
5273 For some caveats with the spelling of @var{symbol}, see also @ref{Macro}.
5276 @section @code{.irpc @var{symbol},@var{values}}@dots{}
5278 @cindex @code{irpc} directive
5279 Evaluate a sequence of statements assigning different values to @var{symbol}.
5280 The sequence of statements starts at the @code{.irpc} directive, and is
5281 terminated by an @code{.endr} directive. For each character in @var{value},
5282 @var{symbol} is set to the character, and the sequence of statements is
5283 assembled. If no @var{value} is listed, the sequence of statements is
5284 assembled once, with @var{symbol} set to the null string. To refer to
5285 @var{symbol} within the sequence of statements, use @var{\symbol}.
5287 For example, assembling
5295 is equivalent to assembling
5303 For some caveats with the spelling of @var{symbol}, see also the discussion
5307 @section @code{.lcomm @var{symbol} , @var{length}}
5309 @cindex @code{lcomm} directive
5310 @cindex local common symbols
5311 @cindex symbols, local common
5312 Reserve @var{length} (an absolute expression) bytes for a local common
5313 denoted by @var{symbol}. The section and value of @var{symbol} are
5314 those of the new local common. The addresses are allocated in the bss
5315 section, so that at run-time the bytes start off zeroed. @var{Symbol}
5316 is not declared global (@pxref{Global,,@code{.global}}), so is normally
5317 not visible to @code{@value{LD}}.
5320 Some targets permit a third argument to be used with @code{.lcomm}. This
5321 argument specifies the desired alignment of the symbol in the bss section.
5325 The syntax for @code{.lcomm} differs slightly on the HPPA. The syntax is
5326 @samp{@var{symbol} .lcomm, @var{length}}; @var{symbol} is optional.
5330 @section @code{.lflags}
5332 @cindex @code{lflags} directive (ignored)
5333 @command{@value{AS}} accepts this directive, for compatibility with other
5334 assemblers, but ignores it.
5336 @ifclear no-line-dir
5338 @section @code{.line @var{line-number}}
5340 @cindex @code{line} directive
5341 @cindex logical line number
5343 Change the logical line number. @var{line-number} must be an absolute
5344 expression. The next line has that logical line number. Therefore any other
5345 statements on the current line (after a statement separator character) are
5346 reported as on logical line number @var{line-number} @minus{} 1. One day
5347 @command{@value{AS}} will no longer support this directive: it is recognized only
5348 for compatibility with existing assembler programs.
5351 Even though this is a directive associated with the @code{a.out} or
5352 @code{b.out} object-code formats, @command{@value{AS}} still recognizes it
5353 when producing COFF output, and treats @samp{.line} as though it
5354 were the COFF @samp{.ln} @emph{if} it is found outside a
5355 @code{.def}/@code{.endef} pair.
5357 Inside a @code{.def}, @samp{.line} is, instead, one of the directives
5358 used by compilers to generate auxiliary symbol information for
5363 @section @code{.linkonce [@var{type}]}
5365 @cindex @code{linkonce} directive
5366 @cindex common sections
5367 Mark the current section so that the linker only includes a single copy of it.
5368 This may be used to include the same section in several different object files,
5369 but ensure that the linker will only include it once in the final output file.
5370 The @code{.linkonce} pseudo-op must be used for each instance of the section.
5371 Duplicate sections are detected based on the section name, so it should be
5374 This directive is only supported by a few object file formats; as of this
5375 writing, the only object file format which supports it is the Portable
5376 Executable format used on Windows NT.
5378 The @var{type} argument is optional. If specified, it must be one of the
5379 following strings. For example:
5383 Not all types may be supported on all object file formats.
5387 Silently discard duplicate sections. This is the default.
5390 Warn if there are duplicate sections, but still keep only one copy.
5393 Warn if any of the duplicates have different sizes.
5396 Warn if any of the duplicates do not have exactly the same contents.
5400 @section @code{.list}
5402 @cindex @code{list} directive
5403 @cindex listing control, turning on
5404 Control (in conjunction with the @code{.nolist} directive) whether or
5405 not assembly listings are generated. These two directives maintain an
5406 internal counter (which is zero initially). @code{.list} increments the
5407 counter, and @code{.nolist} decrements it. Assembly listings are
5408 generated whenever the counter is greater than zero.
5410 By default, listings are disabled. When you enable them (with the
5411 @samp{-a} command line option; @pxref{Invoking,,Command-Line Options}),
5412 the initial value of the listing counter is one.
5415 @section @code{.ln @var{line-number}}
5417 @cindex @code{ln} directive
5418 @ifclear no-line-dir
5419 @samp{.ln} is a synonym for @samp{.line}.
5422 Tell @command{@value{AS}} to change the logical line number. @var{line-number}
5423 must be an absolute expression. The next line has that logical
5424 line number, so any other statements on the current line (after a
5425 statement separator character @code{;}) are reported as on logical
5426 line number @var{line-number} @minus{} 1.
5429 This directive is accepted, but ignored, when @command{@value{AS}} is
5430 configured for @code{b.out}; its effect is only associated with COFF
5436 @section @code{.loc @var{fileno} @var{lineno} [@var{column}] [@var{options}]}
5437 @cindex @code{loc} directive
5438 When emitting DWARF2 line number information,
5439 the @code{.loc} directive will add a row to the @code{.debug_line} line
5440 number matrix corresponding to the immediately following assembly
5441 instruction. The @var{fileno}, @var{lineno}, and optional @var{column}
5442 arguments will be applied to the @code{.debug_line} state machine before
5445 The @var{options} are a sequence of the following tokens in any order:
5449 This option will set the @code{basic_block} register in the
5450 @code{.debug_line} state machine to @code{true}.
5453 This option will set the @code{prologue_end} register in the
5454 @code{.debug_line} state machine to @code{true}.
5456 @item epilogue_begin
5457 This option will set the @code{epilogue_begin} register in the
5458 @code{.debug_line} state machine to @code{true}.
5460 @item is_stmt @var{value}
5461 This option will set the @code{is_stmt} register in the
5462 @code{.debug_line} state machine to @code{value}, which must be
5465 @item isa @var{value}
5466 This directive will set the @code{isa} register in the @code{.debug_line}
5467 state machine to @var{value}, which must be an unsigned integer.
5469 @item discriminator @var{value}
5470 This directive will set the @code{discriminator} register in the @code{.debug_line}
5471 state machine to @var{value}, which must be an unsigned integer.
5475 @node Loc_mark_labels
5476 @section @code{.loc_mark_labels @var{enable}}
5477 @cindex @code{loc_mark_labels} directive
5478 When emitting DWARF2 line number information,
5479 the @code{.loc_mark_labels} directive makes the assembler emit an entry
5480 to the @code{.debug_line} line number matrix with the @code{basic_block}
5481 register in the state machine set whenever a code label is seen.
5482 The @var{enable} argument should be either 1 or 0, to enable or disable
5483 this function respectively.
5487 @section @code{.local @var{names}}
5489 @cindex @code{local} directive
5490 This directive, which is available for ELF targets, marks each symbol in
5491 the comma-separated list of @code{names} as a local symbol so that it
5492 will not be externally visible. If the symbols do not already exist,
5493 they will be created.
5495 For targets where the @code{.lcomm} directive (@pxref{Lcomm}) does not
5496 accept an alignment argument, which is the case for most ELF targets,
5497 the @code{.local} directive can be used in combination with @code{.comm}
5498 (@pxref{Comm}) to define aligned local common data.
5502 @section @code{.long @var{expressions}}
5504 @cindex @code{long} directive
5505 @code{.long} is the same as @samp{.int}. @xref{Int,,@code{.int}}.
5508 @c no one seems to know what this is for or whether this description is
5509 @c what it really ought to do
5511 @section @code{.lsym @var{symbol}, @var{expression}}
5513 @cindex @code{lsym} directive
5514 @cindex symbol, not referenced in assembly
5515 @code{.lsym} creates a new symbol named @var{symbol}, but does not put it in
5516 the hash table, ensuring it cannot be referenced by name during the
5517 rest of the assembly. This sets the attributes of the symbol to be
5518 the same as the expression value:
5520 @var{other} = @var{descriptor} = 0
5521 @var{type} = @r{(section of @var{expression})}
5522 @var{value} = @var{expression}
5525 The new symbol is not flagged as external.
5529 @section @code{.macro}
5532 The commands @code{.macro} and @code{.endm} allow you to define macros that
5533 generate assembly output. For example, this definition specifies a macro
5534 @code{sum} that puts a sequence of numbers into memory:
5537 .macro sum from=0, to=5
5546 With that definition, @samp{SUM 0,5} is equivalent to this assembly input:
5558 @item .macro @var{macname}
5559 @itemx .macro @var{macname} @var{macargs} @dots{}
5560 @cindex @code{macro} directive
5561 Begin the definition of a macro called @var{macname}. If your macro
5562 definition requires arguments, specify their names after the macro name,
5563 separated by commas or spaces. You can qualify the macro argument to
5564 indicate whether all invocations must specify a non-blank value (through
5565 @samp{:@code{req}}), or whether it takes all of the remaining arguments
5566 (through @samp{:@code{vararg}}). You can supply a default value for any
5567 macro argument by following the name with @samp{=@var{deflt}}. You
5568 cannot define two macros with the same @var{macname} unless it has been
5569 subject to the @code{.purgem} directive (@pxref{Purgem}) between the two
5570 definitions. For example, these are all valid @code{.macro} statements:
5574 Begin the definition of a macro called @code{comm}, which takes no
5577 @item .macro plus1 p, p1
5578 @itemx .macro plus1 p p1
5579 Either statement begins the definition of a macro called @code{plus1},
5580 which takes two arguments; within the macro definition, write
5581 @samp{\p} or @samp{\p1} to evaluate the arguments.
5583 @item .macro reserve_str p1=0 p2
5584 Begin the definition of a macro called @code{reserve_str}, with two
5585 arguments. The first argument has a default value, but not the second.
5586 After the definition is complete, you can call the macro either as
5587 @samp{reserve_str @var{a},@var{b}} (with @samp{\p1} evaluating to
5588 @var{a} and @samp{\p2} evaluating to @var{b}), or as @samp{reserve_str
5589 ,@var{b}} (with @samp{\p1} evaluating as the default, in this case
5590 @samp{0}, and @samp{\p2} evaluating to @var{b}).
5592 @item .macro m p1:req, p2=0, p3:vararg
5593 Begin the definition of a macro called @code{m}, with at least three
5594 arguments. The first argument must always have a value specified, but
5595 not the second, which instead has a default value. The third formal
5596 will get assigned all remaining arguments specified at invocation time.
5598 When you call a macro, you can specify the argument values either by
5599 position, or by keyword. For example, @samp{sum 9,17} is equivalent to
5600 @samp{sum to=17, from=9}.
5604 Note that since each of the @var{macargs} can be an identifier exactly
5605 as any other one permitted by the target architecture, there may be
5606 occasional problems if the target hand-crafts special meanings to certain
5607 characters when they occur in a special position. For example, if the colon
5608 (@code{:}) is generally permitted to be part of a symbol name, but the
5609 architecture specific code special-cases it when occurring as the final
5610 character of a symbol (to denote a label), then the macro parameter
5611 replacement code will have no way of knowing that and consider the whole
5612 construct (including the colon) an identifier, and check only this
5613 identifier for being the subject to parameter substitution. So for example
5614 this macro definition:
5622 might not work as expected. Invoking @samp{label foo} might not create a label
5623 called @samp{foo} but instead just insert the text @samp{\l:} into the
5624 assembler source, probably generating an error about an unrecognised
5627 Similarly problems might occur with the period character (@samp{.})
5628 which is often allowed inside opcode names (and hence identifier names). So
5629 for example constructing a macro to build an opcode from a base name and a
5630 length specifier like this:
5633 .macro opcode base length
5638 and invoking it as @samp{opcode store l} will not create a @samp{store.l}
5639 instruction but instead generate some kind of error as the assembler tries to
5640 interpret the text @samp{\base.\length}.
5642 There are several possible ways around this problem:
5645 @item Insert white space
5646 If it is possible to use white space characters then this is the simplest
5655 @item Use @samp{\()}
5656 The string @samp{\()} can be used to separate the end of a macro argument from
5657 the following text. eg:
5660 .macro opcode base length
5665 @item Use the alternate macro syntax mode
5666 In the alternative macro syntax mode the ampersand character (@samp{&}) can be
5667 used as a separator. eg:
5677 Note: this problem of correctly identifying string parameters to pseudo ops
5678 also applies to the identifiers used in @code{.irp} (@pxref{Irp})
5679 and @code{.irpc} (@pxref{Irpc}) as well.
5682 @cindex @code{endm} directive
5683 Mark the end of a macro definition.
5686 @cindex @code{exitm} directive
5687 Exit early from the current macro definition.
5689 @cindex number of macros executed
5690 @cindex macros, count executed
5692 @command{@value{AS}} maintains a counter of how many macros it has
5693 executed in this pseudo-variable; you can copy that number to your
5694 output with @samp{\@@}, but @emph{only within a macro definition}.
5696 @item LOCAL @var{name} [ , @dots{} ]
5697 @emph{Warning: @code{LOCAL} is only available if you select ``alternate
5698 macro syntax'' with @samp{--alternate} or @code{.altmacro}.}
5699 @xref{Altmacro,,@code{.altmacro}}.
5703 @section @code{.mri @var{val}}
5705 @cindex @code{mri} directive
5706 @cindex MRI mode, temporarily
5707 If @var{val} is non-zero, this tells @command{@value{AS}} to enter MRI mode. If
5708 @var{val} is zero, this tells @command{@value{AS}} to exit MRI mode. This change
5709 affects code assembled until the next @code{.mri} directive, or until the end
5710 of the file. @xref{M, MRI mode, MRI mode}.
5713 @section @code{.noaltmacro}
5714 Disable alternate macro mode. @xref{Altmacro}.
5717 @section @code{.nolist}
5719 @cindex @code{nolist} directive
5720 @cindex listing control, turning off
5721 Control (in conjunction with the @code{.list} directive) whether or
5722 not assembly listings are generated. These two directives maintain an
5723 internal counter (which is zero initially). @code{.list} increments the
5724 counter, and @code{.nolist} decrements it. Assembly listings are
5725 generated whenever the counter is greater than zero.
5728 @section @code{.octa @var{bignums}}
5730 @c FIXME: double size emitted for "octa" on i960, others? Or warn?
5731 @cindex @code{octa} directive
5732 @cindex integer, 16-byte
5733 @cindex sixteen byte integer
5734 This directive expects zero or more bignums, separated by commas. For each
5735 bignum, it emits a 16-byte integer.
5737 The term ``octa'' comes from contexts in which a ``word'' is two bytes;
5738 hence @emph{octa}-word for 16 bytes.
5741 @section @code{.offset @var{loc}}
5743 @cindex @code{offset} directive
5744 Set the location counter to @var{loc} in the absolute section. @var{loc} must
5745 be an absolute expression. This directive may be useful for defining
5746 symbols with absolute values. Do not confuse it with the @code{.org}
5750 @section @code{.org @var{new-lc} , @var{fill}}
5752 @cindex @code{org} directive
5753 @cindex location counter, advancing
5754 @cindex advancing location counter
5755 @cindex current address, advancing
5756 Advance the location counter of the current section to
5757 @var{new-lc}. @var{new-lc} is either an absolute expression or an
5758 expression with the same section as the current subsection. That is,
5759 you can't use @code{.org} to cross sections: if @var{new-lc} has the
5760 wrong section, the @code{.org} directive is ignored. To be compatible
5761 with former assemblers, if the section of @var{new-lc} is absolute,
5762 @command{@value{AS}} issues a warning, then pretends the section of @var{new-lc}
5763 is the same as the current subsection.
5765 @code{.org} may only increase the location counter, or leave it
5766 unchanged; you cannot use @code{.org} to move the location counter
5769 @c double negative used below "not undefined" because this is a specific
5770 @c reference to "undefined" (as SEG_UNKNOWN is called in this manual)
5771 @c section. doc@cygnus.com 18feb91
5772 Because @command{@value{AS}} tries to assemble programs in one pass, @var{new-lc}
5773 may not be undefined. If you really detest this restriction we eagerly await
5774 a chance to share your improved assembler.
5776 Beware that the origin is relative to the start of the section, not
5777 to the start of the subsection. This is compatible with other
5778 people's assemblers.
5780 When the location counter (of the current subsection) is advanced, the
5781 intervening bytes are filled with @var{fill} which should be an
5782 absolute expression. If the comma and @var{fill} are omitted,
5783 @var{fill} defaults to zero.
5786 @section @code{.p2align[wl] @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
5788 @cindex padding the location counter given a power of two
5789 @cindex @code{p2align} directive
5790 Pad the location counter (in the current subsection) to a particular
5791 storage boundary. The first expression (which must be absolute) is the
5792 number of low-order zero bits the location counter must have after
5793 advancement. For example @samp{.p2align 3} advances the location
5794 counter until it a multiple of 8. If the location counter is already a
5795 multiple of 8, no change is needed.
5797 The second expression (also absolute) gives the fill value to be stored in the
5798 padding bytes. It (and the comma) may be omitted. If it is omitted, the
5799 padding bytes are normally zero. However, on some systems, if the section is
5800 marked as containing code and the fill value is omitted, the space is filled
5801 with no-op instructions.
5803 The third expression is also absolute, and is also optional. If it is present,
5804 it is the maximum number of bytes that should be skipped by this alignment
5805 directive. If doing the alignment would require skipping more bytes than the
5806 specified maximum, then the alignment is not done at all. You can omit the
5807 fill value (the second argument) entirely by simply using two commas after the
5808 required alignment; this can be useful if you want the alignment to be filled
5809 with no-op instructions when appropriate.
5811 @cindex @code{p2alignw} directive
5812 @cindex @code{p2alignl} directive
5813 The @code{.p2alignw} and @code{.p2alignl} directives are variants of the
5814 @code{.p2align} directive. The @code{.p2alignw} directive treats the fill
5815 pattern as a two byte word value. The @code{.p2alignl} directives treats the
5816 fill pattern as a four byte longword value. For example, @code{.p2alignw
5817 2,0x368d} will align to a multiple of 4. If it skips two bytes, they will be
5818 filled in with the value 0x368d (the exact placement of the bytes depends upon
5819 the endianness of the processor). If it skips 1 or 3 bytes, the fill value is
5824 @section @code{.popsection}
5826 @cindex @code{popsection} directive
5827 @cindex Section Stack
5828 This is one of the ELF section stack manipulation directives. The others are
5829 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
5830 @code{.pushsection} (@pxref{PushSection}), and @code{.previous}
5833 This directive replaces the current section (and subsection) with the top
5834 section (and subsection) on the section stack. This section is popped off the
5840 @section @code{.previous}
5842 @cindex @code{previous} directive
5843 @cindex Section Stack
5844 This is one of the ELF section stack manipulation directives. The others are
5845 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
5846 @code{.pushsection} (@pxref{PushSection}), and @code{.popsection}
5847 (@pxref{PopSection}).
5849 This directive swaps the current section (and subsection) with most recently
5850 referenced section/subsection pair prior to this one. Multiple
5851 @code{.previous} directives in a row will flip between two sections (and their
5852 subsections). For example:
5864 Will place 0x1234 and 0x9abc into subsection 1 and 0x5678 into subsection 2 of
5870 # Now in section A subsection 1
5874 # Now in section B subsection 0
5877 # Now in section B subsection 1
5880 # Now in section B subsection 0
5884 Will place 0x1234 into section A, 0x5678 and 0xdef0 into subsection 0 of
5885 section B and 0x9abc into subsection 1 of section B.
5887 In terms of the section stack, this directive swaps the current section with
5888 the top section on the section stack.
5892 @section @code{.print @var{string}}
5894 @cindex @code{print} directive
5895 @command{@value{AS}} will print @var{string} on the standard output during
5896 assembly. You must put @var{string} in double quotes.
5900 @section @code{.protected @var{names}}
5902 @cindex @code{protected} directive
5904 This is one of the ELF visibility directives. The other two are
5905 @code{.hidden} (@pxref{Hidden}) and @code{.internal} (@pxref{Internal}).
5907 This directive overrides the named symbols default visibility (which is set by
5908 their binding: local, global or weak). The directive sets the visibility to
5909 @code{protected} which means that any references to the symbols from within the
5910 components that defines them must be resolved to the definition in that
5911 component, even if a definition in another component would normally preempt
5916 @section @code{.psize @var{lines} , @var{columns}}
5918 @cindex @code{psize} directive
5919 @cindex listing control: paper size
5920 @cindex paper size, for listings
5921 Use this directive to declare the number of lines---and, optionally, the
5922 number of columns---to use for each page, when generating listings.
5924 If you do not use @code{.psize}, listings use a default line-count
5925 of 60. You may omit the comma and @var{columns} specification; the
5926 default width is 200 columns.
5928 @command{@value{AS}} generates formfeeds whenever the specified number of
5929 lines is exceeded (or whenever you explicitly request one, using
5932 If you specify @var{lines} as @code{0}, no formfeeds are generated save
5933 those explicitly specified with @code{.eject}.
5936 @section @code{.purgem @var{name}}
5938 @cindex @code{purgem} directive
5939 Undefine the macro @var{name}, so that later uses of the string will not be
5940 expanded. @xref{Macro}.
5944 @section @code{.pushsection @var{name} [, @var{subsection}] [, "@var{flags}"[, @@@var{type}[,@var{arguments}]]]}
5946 @cindex @code{pushsection} directive
5947 @cindex Section Stack
5948 This is one of the ELF section stack manipulation directives. The others are
5949 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
5950 @code{.popsection} (@pxref{PopSection}), and @code{.previous}
5953 This directive pushes the current section (and subsection) onto the
5954 top of the section stack, and then replaces the current section and
5955 subsection with @code{name} and @code{subsection}. The optional
5956 @code{flags}, @code{type} and @code{arguments} are treated the same
5957 as in the @code{.section} (@pxref{Section}) directive.
5961 @section @code{.quad @var{bignums}}
5963 @cindex @code{quad} directive
5964 @code{.quad} expects zero or more bignums, separated by commas. For
5965 each bignum, it emits
5967 an 8-byte integer. If the bignum won't fit in 8 bytes, it prints a
5968 warning message; and just takes the lowest order 8 bytes of the bignum.
5969 @cindex eight-byte integer
5970 @cindex integer, 8-byte
5972 The term ``quad'' comes from contexts in which a ``word'' is two bytes;
5973 hence @emph{quad}-word for 8 bytes.
5976 a 16-byte integer. If the bignum won't fit in 16 bytes, it prints a
5977 warning message; and just takes the lowest order 16 bytes of the bignum.
5978 @cindex sixteen-byte integer
5979 @cindex integer, 16-byte
5983 @section @code{.reloc @var{offset}, @var{reloc_name}[, @var{expression}]}
5985 @cindex @code{reloc} directive
5986 Generate a relocation at @var{offset} of type @var{reloc_name} with value
5987 @var{expression}. If @var{offset} is a number, the relocation is generated in
5988 the current section. If @var{offset} is an expression that resolves to a
5989 symbol plus offset, the relocation is generated in the given symbol's section.
5990 @var{expression}, if present, must resolve to a symbol plus addend or to an
5991 absolute value, but note that not all targets support an addend. e.g. ELF REL
5992 targets such as i386 store an addend in the section contents rather than in the
5993 relocation. This low level interface does not support addends stored in the
5997 @section @code{.rept @var{count}}
5999 @cindex @code{rept} directive
6000 Repeat the sequence of lines between the @code{.rept} directive and the next
6001 @code{.endr} directive @var{count} times.
6003 For example, assembling
6011 is equivalent to assembling
6020 @section @code{.sbttl "@var{subheading}"}
6022 @cindex @code{sbttl} directive
6023 @cindex subtitles for listings
6024 @cindex listing control: subtitle
6025 Use @var{subheading} as the title (third line, immediately after the
6026 title line) when generating assembly listings.
6028 This directive affects subsequent pages, as well as the current page if
6029 it appears within ten lines of the top of a page.
6033 @section @code{.scl @var{class}}
6035 @cindex @code{scl} directive
6036 @cindex symbol storage class (COFF)
6037 @cindex COFF symbol storage class
6038 Set the storage-class value for a symbol. This directive may only be
6039 used inside a @code{.def}/@code{.endef} pair. Storage class may flag
6040 whether a symbol is static or external, or it may record further
6041 symbolic debugging information.
6044 The @samp{.scl} directive is primarily associated with COFF output; when
6045 configured to generate @code{b.out} output format, @command{@value{AS}}
6046 accepts this directive but ignores it.
6052 @section @code{.section @var{name}}
6054 @cindex named section
6055 Use the @code{.section} directive to assemble the following code into a section
6058 This directive is only supported for targets that actually support arbitrarily
6059 named sections; on @code{a.out} targets, for example, it is not accepted, even
6060 with a standard @code{a.out} section name.
6064 @c only print the extra heading if both COFF and ELF are set
6065 @subheading COFF Version
6068 @cindex @code{section} directive (COFF version)
6069 For COFF targets, the @code{.section} directive is used in one of the following
6073 .section @var{name}[, "@var{flags}"]
6074 .section @var{name}[, @var{subsection}]
6077 If the optional argument is quoted, it is taken as flags to use for the
6078 section. Each flag is a single character. The following flags are recognized:
6081 bss section (uninitialized data)
6083 section is not loaded
6089 exclude section from linking
6095 shared section (meaningful for PE targets)
6097 ignored. (For compatibility with the ELF version)
6099 section is not readable (meaningful for PE targets)
6101 single-digit power-of-two section alignment (GNU extension)
6104 If no flags are specified, the default flags depend upon the section name. If
6105 the section name is not recognized, the default will be for the section to be
6106 loaded and writable. Note the @code{n} and @code{w} flags remove attributes
6107 from the section, rather than adding them, so if they are used on their own it
6108 will be as if no flags had been specified at all.
6110 If the optional argument to the @code{.section} directive is not quoted, it is
6111 taken as a subsection number (@pxref{Sub-Sections}).
6116 @c only print the extra heading if both COFF and ELF are set
6117 @subheading ELF Version
6120 @cindex Section Stack
6121 This is one of the ELF section stack manipulation directives. The others are
6122 @code{.subsection} (@pxref{SubSection}), @code{.pushsection}
6123 (@pxref{PushSection}), @code{.popsection} (@pxref{PopSection}), and
6124 @code{.previous} (@pxref{Previous}).
6126 @cindex @code{section} directive (ELF version)
6127 For ELF targets, the @code{.section} directive is used like this:
6130 .section @var{name} [, "@var{flags}"[, @@@var{type}[,@var{flag_specific_arguments}]]]
6133 The optional @var{flags} argument is a quoted string which may contain any
6134 combination of the following characters:
6137 section is allocatable
6139 section is excluded from executable and shared library.
6143 section is executable
6145 section is mergeable
6147 section contains zero terminated strings
6149 section is a member of a section group
6151 section is used for thread-local-storage
6153 section is a member of the previously-current section's group, if any
6156 The optional @var{type} argument may contain one of the following constants:
6159 section contains data
6161 section does not contain data (i.e., section only occupies space)
6163 section contains data which is used by things other than the program
6165 section contains an array of pointers to init functions
6167 section contains an array of pointers to finish functions
6168 @item @@preinit_array
6169 section contains an array of pointers to pre-init functions
6172 Many targets only support the first three section types.
6174 Note on targets where the @code{@@} character is the start of a comment (eg
6175 ARM) then another character is used instead. For example the ARM port uses the
6178 If @var{flags} contains the @code{M} symbol then the @var{type} argument must
6179 be specified as well as an extra argument---@var{entsize}---like this:
6182 .section @var{name} , "@var{flags}"M, @@@var{type}, @var{entsize}
6185 Sections with the @code{M} flag but not @code{S} flag must contain fixed size
6186 constants, each @var{entsize} octets long. Sections with both @code{M} and
6187 @code{S} must contain zero terminated strings where each character is
6188 @var{entsize} bytes long. The linker may remove duplicates within sections with
6189 the same name, same entity size and same flags. @var{entsize} must be an
6190 absolute expression. For sections with both @code{M} and @code{S}, a string
6191 which is a suffix of a larger string is considered a duplicate. Thus
6192 @code{"def"} will be merged with @code{"abcdef"}; A reference to the first
6193 @code{"def"} will be changed to a reference to @code{"abcdef"+3}.
6195 If @var{flags} contains the @code{G} symbol then the @var{type} argument must
6196 be present along with an additional field like this:
6199 .section @var{name} , "@var{flags}"G, @@@var{type}, @var{GroupName}[, @var{linkage}]
6202 The @var{GroupName} field specifies the name of the section group to which this
6203 particular section belongs. The optional linkage field can contain:
6206 indicates that only one copy of this section should be retained
6211 Note: if both the @var{M} and @var{G} flags are present then the fields for
6212 the Merge flag should come first, like this:
6215 .section @var{name} , "@var{flags}"MG, @@@var{type}, @var{entsize}, @var{GroupName}[, @var{linkage}]
6218 If @var{flags} contains the @code{?} symbol then it may not also contain the
6219 @code{G} symbol and the @var{GroupName} or @var{linkage} fields should not be
6220 present. Instead, @code{?} says to consider the section that's current before
6221 this directive. If that section used @code{G}, then the new section will use
6222 @code{G} with those same @var{GroupName} and @var{linkage} fields implicitly.
6223 If not, then the @code{?} symbol has no effect.
6225 If no flags are specified, the default flags depend upon the section name. If
6226 the section name is not recognized, the default will be for the section to have
6227 none of the above flags: it will not be allocated in memory, nor writable, nor
6228 executable. The section will contain data.
6230 For ELF targets, the assembler supports another type of @code{.section}
6231 directive for compatibility with the Solaris assembler:
6234 .section "@var{name}"[, @var{flags}...]
6237 Note that the section name is quoted. There may be a sequence of comma
6241 section is allocatable
6245 section is executable
6247 section is excluded from executable and shared library.
6249 section is used for thread local storage
6252 This directive replaces the current section and subsection. See the
6253 contents of the gas testsuite directory @code{gas/testsuite/gas/elf} for
6254 some examples of how this directive and the other section stack directives
6260 @section @code{.set @var{symbol}, @var{expression}}
6262 @cindex @code{set} directive
6263 @cindex symbol value, setting
6264 Set the value of @var{symbol} to @var{expression}. This
6265 changes @var{symbol}'s value and type to conform to
6266 @var{expression}. If @var{symbol} was flagged as external, it remains
6267 flagged (@pxref{Symbol Attributes}).
6269 You may @code{.set} a symbol many times in the same assembly.
6271 If you @code{.set} a global symbol, the value stored in the object
6272 file is the last value stored into it.
6275 On Z80 @code{set} is a real instruction, use
6276 @samp{@var{symbol} defl @var{expression}} instead.
6280 @section @code{.short @var{expressions}}
6282 @cindex @code{short} directive
6284 @code{.short} is normally the same as @samp{.word}.
6285 @xref{Word,,@code{.word}}.
6287 In some configurations, however, @code{.short} and @code{.word} generate
6288 numbers of different lengths. @xref{Machine Dependencies}.
6292 @code{.short} is the same as @samp{.word}. @xref{Word,,@code{.word}}.
6295 This expects zero or more @var{expressions}, and emits
6296 a 16 bit number for each.
6301 @section @code{.single @var{flonums}}
6303 @cindex @code{single} directive
6304 @cindex floating point numbers (single)
6305 This directive assembles zero or more flonums, separated by commas. It
6306 has the same effect as @code{.float}.
6308 The exact kind of floating point numbers emitted depends on how
6309 @command{@value{AS}} is configured. @xref{Machine Dependencies}.
6313 On the @value{TARGET} family, @code{.single} emits 32-bit floating point
6314 numbers in @sc{ieee} format.
6320 @section @code{.size}
6322 This directive is used to set the size associated with a symbol.
6326 @c only print the extra heading if both COFF and ELF are set
6327 @subheading COFF Version
6330 @cindex @code{size} directive (COFF version)
6331 For COFF targets, the @code{.size} directive is only permitted inside
6332 @code{.def}/@code{.endef} pairs. It is used like this:
6335 .size @var{expression}
6339 @samp{.size} is only meaningful when generating COFF format output; when
6340 @command{@value{AS}} is generating @code{b.out}, it accepts this directive but
6347 @c only print the extra heading if both COFF and ELF are set
6348 @subheading ELF Version
6351 @cindex @code{size} directive (ELF version)
6352 For ELF targets, the @code{.size} directive is used like this:
6355 .size @var{name} , @var{expression}
6358 This directive sets the size associated with a symbol @var{name}.
6359 The size in bytes is computed from @var{expression} which can make use of label
6360 arithmetic. This directive is typically used to set the size of function
6365 @ifclear no-space-dir
6367 @section @code{.skip @var{size} , @var{fill}}
6369 @cindex @code{skip} directive
6370 @cindex filling memory
6371 This directive emits @var{size} bytes, each of value @var{fill}. Both
6372 @var{size} and @var{fill} are absolute expressions. If the comma and
6373 @var{fill} are omitted, @var{fill} is assumed to be zero. This is the same as
6378 @section @code{.sleb128 @var{expressions}}
6380 @cindex @code{sleb128} directive
6381 @var{sleb128} stands for ``signed little endian base 128.'' This is a
6382 compact, variable length representation of numbers used by the DWARF
6383 symbolic debugging format. @xref{Uleb128, ,@code{.uleb128}}.
6385 @ifclear no-space-dir
6387 @section @code{.space @var{size} , @var{fill}}
6389 @cindex @code{space} directive
6390 @cindex filling memory
6391 This directive emits @var{size} bytes, each of value @var{fill}. Both
6392 @var{size} and @var{fill} are absolute expressions. If the comma
6393 and @var{fill} are omitted, @var{fill} is assumed to be zero. This is the same
6398 @emph{Warning:} @code{.space} has a completely different meaning for HPPA
6399 targets; use @code{.block} as a substitute. See @cite{HP9000 Series 800
6400 Assembly Language Reference Manual} (HP 92432-90001) for the meaning of the
6401 @code{.space} directive. @xref{HPPA Directives,,HPPA Assembler Directives},
6409 @section @code{.stabd, .stabn, .stabs}
6411 @cindex symbolic debuggers, information for
6412 @cindex @code{stab@var{x}} directives
6413 There are three directives that begin @samp{.stab}.
6414 All emit symbols (@pxref{Symbols}), for use by symbolic debuggers.
6415 The symbols are not entered in the @command{@value{AS}} hash table: they
6416 cannot be referenced elsewhere in the source file.
6417 Up to five fields are required:
6421 This is the symbol's name. It may contain any character except
6422 @samp{\000}, so is more general than ordinary symbol names. Some
6423 debuggers used to code arbitrarily complex structures into symbol names
6427 An absolute expression. The symbol's type is set to the low 8 bits of
6428 this expression. Any bit pattern is permitted, but @code{@value{LD}}
6429 and debuggers choke on silly bit patterns.
6432 An absolute expression. The symbol's ``other'' attribute is set to the
6433 low 8 bits of this expression.
6436 An absolute expression. The symbol's descriptor is set to the low 16
6437 bits of this expression.
6440 An absolute expression which becomes the symbol's value.
6443 If a warning is detected while reading a @code{.stabd}, @code{.stabn},
6444 or @code{.stabs} statement, the symbol has probably already been created;
6445 you get a half-formed symbol in your object file. This is
6446 compatible with earlier assemblers!
6449 @cindex @code{stabd} directive
6450 @item .stabd @var{type} , @var{other} , @var{desc}
6452 The ``name'' of the symbol generated is not even an empty string.
6453 It is a null pointer, for compatibility. Older assemblers used a
6454 null pointer so they didn't waste space in object files with empty
6457 The symbol's value is set to the location counter,
6458 relocatably. When your program is linked, the value of this symbol
6459 is the address of the location counter when the @code{.stabd} was
6462 @cindex @code{stabn} directive
6463 @item .stabn @var{type} , @var{other} , @var{desc} , @var{value}
6464 The name of the symbol is set to the empty string @code{""}.
6466 @cindex @code{stabs} directive
6467 @item .stabs @var{string} , @var{type} , @var{other} , @var{desc} , @var{value}
6468 All five fields are specified.
6474 @section @code{.string} "@var{str}", @code{.string8} "@var{str}", @code{.string16}
6475 "@var{str}", @code{.string32} "@var{str}", @code{.string64} "@var{str}"
6477 @cindex string, copying to object file
6478 @cindex string8, copying to object file
6479 @cindex string16, copying to object file
6480 @cindex string32, copying to object file
6481 @cindex string64, copying to object file
6482 @cindex @code{string} directive
6483 @cindex @code{string8} directive
6484 @cindex @code{string16} directive
6485 @cindex @code{string32} directive
6486 @cindex @code{string64} directive
6488 Copy the characters in @var{str} to the object file. You may specify more than
6489 one string to copy, separated by commas. Unless otherwise specified for a
6490 particular machine, the assembler marks the end of each string with a 0 byte.
6491 You can use any of the escape sequences described in @ref{Strings,,Strings}.
6493 The variants @code{string16}, @code{string32} and @code{string64} differ from
6494 the @code{string} pseudo opcode in that each 8-bit character from @var{str} is
6495 copied and expanded to 16, 32 or 64 bits respectively. The expanded characters
6496 are stored in target endianness byte order.
6502 .string "B\0\0\0Y\0\0\0E\0\0\0" /* On little endian targets. */
6503 .string "\0\0\0B\0\0\0Y\0\0\0E" /* On big endian targets. */
6508 @section @code{.struct @var{expression}}
6510 @cindex @code{struct} directive
6511 Switch to the absolute section, and set the section offset to @var{expression},
6512 which must be an absolute expression. You might use this as follows:
6521 This would define the symbol @code{field1} to have the value 0, the symbol
6522 @code{field2} to have the value 4, and the symbol @code{field3} to have the
6523 value 8. Assembly would be left in the absolute section, and you would need to
6524 use a @code{.section} directive of some sort to change to some other section
6525 before further assembly.
6529 @section @code{.subsection @var{name}}
6531 @cindex @code{subsection} directive
6532 @cindex Section Stack
6533 This is one of the ELF section stack manipulation directives. The others are
6534 @code{.section} (@pxref{Section}), @code{.pushsection} (@pxref{PushSection}),
6535 @code{.popsection} (@pxref{PopSection}), and @code{.previous}
6538 This directive replaces the current subsection with @code{name}. The current
6539 section is not changed. The replaced subsection is put onto the section stack
6540 in place of the then current top of stack subsection.
6545 @section @code{.symver}
6546 @cindex @code{symver} directive
6547 @cindex symbol versioning
6548 @cindex versions of symbols
6549 Use the @code{.symver} directive to bind symbols to specific version nodes
6550 within a source file. This is only supported on ELF platforms, and is
6551 typically used when assembling files to be linked into a shared library.
6552 There are cases where it may make sense to use this in objects to be bound
6553 into an application itself so as to override a versioned symbol from a
6556 For ELF targets, the @code{.symver} directive can be used like this:
6558 .symver @var{name}, @var{name2@@nodename}
6560 If the symbol @var{name} is defined within the file
6561 being assembled, the @code{.symver} directive effectively creates a symbol
6562 alias with the name @var{name2@@nodename}, and in fact the main reason that we
6563 just don't try and create a regular alias is that the @var{@@} character isn't
6564 permitted in symbol names. The @var{name2} part of the name is the actual name
6565 of the symbol by which it will be externally referenced. The name @var{name}
6566 itself is merely a name of convenience that is used so that it is possible to
6567 have definitions for multiple versions of a function within a single source
6568 file, and so that the compiler can unambiguously know which version of a
6569 function is being mentioned. The @var{nodename} portion of the alias should be
6570 the name of a node specified in the version script supplied to the linker when
6571 building a shared library. If you are attempting to override a versioned
6572 symbol from a shared library, then @var{nodename} should correspond to the
6573 nodename of the symbol you are trying to override.
6575 If the symbol @var{name} is not defined within the file being assembled, all
6576 references to @var{name} will be changed to @var{name2@@nodename}. If no
6577 reference to @var{name} is made, @var{name2@@nodename} will be removed from the
6580 Another usage of the @code{.symver} directive is:
6582 .symver @var{name}, @var{name2@@@@nodename}
6584 In this case, the symbol @var{name} must exist and be defined within
6585 the file being assembled. It is similar to @var{name2@@nodename}. The
6586 difference is @var{name2@@@@nodename} will also be used to resolve
6587 references to @var{name2} by the linker.
6589 The third usage of the @code{.symver} directive is:
6591 .symver @var{name}, @var{name2@@@@@@nodename}
6593 When @var{name} is not defined within the
6594 file being assembled, it is treated as @var{name2@@nodename}. When
6595 @var{name} is defined within the file being assembled, the symbol
6596 name, @var{name}, will be changed to @var{name2@@@@nodename}.
6601 @section @code{.tag @var{structname}}
6603 @cindex COFF structure debugging
6604 @cindex structure debugging, COFF
6605 @cindex @code{tag} directive
6606 This directive is generated by compilers to include auxiliary debugging
6607 information in the symbol table. It is only permitted inside
6608 @code{.def}/@code{.endef} pairs. Tags are used to link structure
6609 definitions in the symbol table with instances of those structures.
6612 @samp{.tag} is only used when generating COFF format output; when
6613 @command{@value{AS}} is generating @code{b.out}, it accepts this directive but
6619 @section @code{.text @var{subsection}}
6621 @cindex @code{text} directive
6622 Tells @command{@value{AS}} to assemble the following statements onto the end of
6623 the text subsection numbered @var{subsection}, which is an absolute
6624 expression. If @var{subsection} is omitted, subsection number zero
6628 @section @code{.title "@var{heading}"}
6630 @cindex @code{title} directive
6631 @cindex listing control: title line
6632 Use @var{heading} as the title (second line, immediately after the
6633 source file name and pagenumber) when generating assembly listings.
6635 This directive affects subsequent pages, as well as the current page if
6636 it appears within ten lines of the top of a page.
6640 @section @code{.type}
6642 This directive is used to set the type of a symbol.
6646 @c only print the extra heading if both COFF and ELF are set
6647 @subheading COFF Version
6650 @cindex COFF symbol type
6651 @cindex symbol type, COFF
6652 @cindex @code{type} directive (COFF version)
6653 For COFF targets, this directive is permitted only within
6654 @code{.def}/@code{.endef} pairs. It is used like this:
6660 This records the integer @var{int} as the type attribute of a symbol table
6664 @samp{.type} is associated only with COFF format output; when
6665 @command{@value{AS}} is configured for @code{b.out} output, it accepts this
6666 directive but ignores it.
6672 @c only print the extra heading if both COFF and ELF are set
6673 @subheading ELF Version
6676 @cindex ELF symbol type
6677 @cindex symbol type, ELF
6678 @cindex @code{type} directive (ELF version)
6679 For ELF targets, the @code{.type} directive is used like this:
6682 .type @var{name} , @var{type description}
6685 This sets the type of symbol @var{name} to be either a
6686 function symbol or an object symbol. There are five different syntaxes
6687 supported for the @var{type description} field, in order to provide
6688 compatibility with various other assemblers.
6690 Because some of the characters used in these syntaxes (such as @samp{@@} and
6691 @samp{#}) are comment characters for some architectures, some of the syntaxes
6692 below do not work on all architectures. The first variant will be accepted by
6693 the GNU assembler on all architectures so that variant should be used for
6694 maximum portability, if you do not need to assemble your code with other
6697 The syntaxes supported are:
6700 .type <name> STT_<TYPE_IN_UPPER_CASE>
6701 .type <name>,#<type>
6702 .type <name>,@@<type>
6703 .type <name>,%<type>
6704 .type <name>,"<type>"
6707 The types supported are:
6712 Mark the symbol as being a function name.
6715 @itemx gnu_indirect_function
6716 Mark the symbol as an indirect function when evaluated during reloc
6717 processing. (This is only supported on assemblers targeting GNU systems).
6721 Mark the symbol as being a data object.
6725 Mark the symbol as being a thead-local data object.
6729 Mark the symbol as being a common data object.
6733 Does not mark the symbol in any way. It is supported just for completeness.
6735 @item gnu_unique_object
6736 Marks the symbol as being a globally unique data object. The dynamic linker
6737 will make sure that in the entire process there is just one symbol with this
6738 name and type in use. (This is only supported on assemblers targeting GNU
6743 Note: Some targets support extra types in addition to those listed above.
6749 @section @code{.uleb128 @var{expressions}}
6751 @cindex @code{uleb128} directive
6752 @var{uleb128} stands for ``unsigned little endian base 128.'' This is a
6753 compact, variable length representation of numbers used by the DWARF
6754 symbolic debugging format. @xref{Sleb128, ,@code{.sleb128}}.
6758 @section @code{.val @var{addr}}
6760 @cindex @code{val} directive
6761 @cindex COFF value attribute
6762 @cindex value attribute, COFF
6763 This directive, permitted only within @code{.def}/@code{.endef} pairs,
6764 records the address @var{addr} as the value attribute of a symbol table
6768 @samp{.val} is used only for COFF output; when @command{@value{AS}} is
6769 configured for @code{b.out}, it accepts this directive but ignores it.
6775 @section @code{.version "@var{string}"}
6777 @cindex @code{version} directive
6778 This directive creates a @code{.note} section and places into it an ELF
6779 formatted note of type NT_VERSION. The note's name is set to @code{string}.
6784 @section @code{.vtable_entry @var{table}, @var{offset}}
6786 @cindex @code{vtable_entry} directive
6787 This directive finds or creates a symbol @code{table} and creates a
6788 @code{VTABLE_ENTRY} relocation for it with an addend of @code{offset}.
6791 @section @code{.vtable_inherit @var{child}, @var{parent}}
6793 @cindex @code{vtable_inherit} directive
6794 This directive finds the symbol @code{child} and finds or creates the symbol
6795 @code{parent} and then creates a @code{VTABLE_INHERIT} relocation for the
6796 parent whose addend is the value of the child symbol. As a special case the
6797 parent name of @code{0} is treated as referring to the @code{*ABS*} section.
6801 @section @code{.warning "@var{string}"}
6802 @cindex warning directive
6803 Similar to the directive @code{.error}
6804 (@pxref{Error,,@code{.error "@var{string}"}}), but just emits a warning.
6807 @section @code{.weak @var{names}}
6809 @cindex @code{weak} directive
6810 This directive sets the weak attribute on the comma separated list of symbol
6811 @code{names}. If the symbols do not already exist, they will be created.
6813 On COFF targets other than PE, weak symbols are a GNU extension. This
6814 directive sets the weak attribute on the comma separated list of symbol
6815 @code{names}. If the symbols do not already exist, they will be created.
6817 On the PE target, weak symbols are supported natively as weak aliases.
6818 When a weak symbol is created that is not an alias, GAS creates an
6819 alternate symbol to hold the default value.
6822 @section @code{.weakref @var{alias}, @var{target}}
6824 @cindex @code{weakref} directive
6825 This directive creates an alias to the target symbol that enables the symbol to
6826 be referenced with weak-symbol semantics, but without actually making it weak.
6827 If direct references or definitions of the symbol are present, then the symbol
6828 will not be weak, but if all references to it are through weak references, the
6829 symbol will be marked as weak in the symbol table.
6831 The effect is equivalent to moving all references to the alias to a separate
6832 assembly source file, renaming the alias to the symbol in it, declaring the
6833 symbol as weak there, and running a reloadable link to merge the object files
6834 resulting from the assembly of the new source file and the old source file that
6835 had the references to the alias removed.
6837 The alias itself never makes to the symbol table, and is entirely handled
6838 within the assembler.
6841 @section @code{.word @var{expressions}}
6843 @cindex @code{word} directive
6844 This directive expects zero or more @var{expressions}, of any section,
6845 separated by commas.
6848 For each expression, @command{@value{AS}} emits a 32-bit number.
6851 For each expression, @command{@value{AS}} emits a 16-bit number.
6856 The size of the number emitted, and its byte order,
6857 depend on what target computer the assembly is for.
6860 @c on amd29k, i960, sparc the "special treatment to support compilers" doesn't
6861 @c happen---32-bit addressability, period; no long/short jumps.
6862 @ifset DIFF-TBL-KLUGE
6863 @cindex difference tables altered
6864 @cindex altered difference tables
6866 @emph{Warning: Special Treatment to support Compilers}
6870 Machines with a 32-bit address space, but that do less than 32-bit
6871 addressing, require the following special treatment. If the machine of
6872 interest to you does 32-bit addressing (or doesn't require it;
6873 @pxref{Machine Dependencies}), you can ignore this issue.
6876 In order to assemble compiler output into something that works,
6877 @command{@value{AS}} occasionally does strange things to @samp{.word} directives.
6878 Directives of the form @samp{.word sym1-sym2} are often emitted by
6879 compilers as part of jump tables. Therefore, when @command{@value{AS}} assembles a
6880 directive of the form @samp{.word sym1-sym2}, and the difference between
6881 @code{sym1} and @code{sym2} does not fit in 16 bits, @command{@value{AS}}
6882 creates a @dfn{secondary jump table}, immediately before the next label.
6883 This secondary jump table is preceded by a short-jump to the
6884 first byte after the secondary table. This short-jump prevents the flow
6885 of control from accidentally falling into the new table. Inside the
6886 table is a long-jump to @code{sym2}. The original @samp{.word}
6887 contains @code{sym1} minus the address of the long-jump to
6890 If there were several occurrences of @samp{.word sym1-sym2} before the
6891 secondary jump table, all of them are adjusted. If there was a
6892 @samp{.word sym3-sym4}, that also did not fit in sixteen bits, a
6893 long-jump to @code{sym4} is included in the secondary jump table,
6894 and the @code{.word} directives are adjusted to contain @code{sym3}
6895 minus the address of the long-jump to @code{sym4}; and so on, for as many
6896 entries in the original jump table as necessary.
6899 @emph{This feature may be disabled by compiling @command{@value{AS}} with the
6900 @samp{-DWORKING_DOT_WORD} option.} This feature is likely to confuse
6901 assembly language programmers.
6904 @c end DIFF-TBL-KLUGE
6907 @section Deprecated Directives
6909 @cindex deprecated directives
6910 @cindex obsolescent directives
6911 One day these directives won't work.
6912 They are included for compatibility with older assemblers.
6919 @node Object Attributes
6920 @chapter Object Attributes
6921 @cindex object attributes
6923 @command{@value{AS}} assembles source files written for a specific architecture
6924 into object files for that architecture. But not all object files are alike.
6925 Many architectures support incompatible variations. For instance, floating
6926 point arguments might be passed in floating point registers if the object file
6927 requires hardware floating point support---or floating point arguments might be
6928 passed in integer registers if the object file supports processors with no
6929 hardware floating point unit. Or, if two objects are built for different
6930 generations of the same architecture, the combination may require the
6931 newer generation at run-time.
6933 This information is useful during and after linking. At link time,
6934 @command{@value{LD}} can warn about incompatible object files. After link
6935 time, tools like @command{gdb} can use it to process the linked file
6938 Compatibility information is recorded as a series of object attributes. Each
6939 attribute has a @dfn{vendor}, @dfn{tag}, and @dfn{value}. The vendor is a
6940 string, and indicates who sets the meaning of the tag. The tag is an integer,
6941 and indicates what property the attribute describes. The value may be a string
6942 or an integer, and indicates how the property affects this object. Missing
6943 attributes are the same as attributes with a zero value or empty string value.
6945 Object attributes were developed as part of the ABI for the ARM Architecture.
6946 The file format is documented in @cite{ELF for the ARM Architecture}.
6949 * GNU Object Attributes:: @sc{gnu} Object Attributes
6950 * Defining New Object Attributes:: Defining New Object Attributes
6953 @node GNU Object Attributes
6954 @section @sc{gnu} Object Attributes
6956 The @code{.gnu_attribute} directive records an object attribute
6957 with vendor @samp{gnu}.
6959 Except for @samp{Tag_compatibility}, which has both an integer and a string for
6960 its value, @sc{gnu} attributes have a string value if the tag number is odd and
6961 an integer value if the tag number is even. The second bit (@code{@var{tag} &
6962 2} is set for architecture-independent attributes and clear for
6963 architecture-dependent ones.
6965 @subsection Common @sc{gnu} attributes
6967 These attributes are valid on all architectures.
6970 @item Tag_compatibility (32)
6971 The compatibility attribute takes an integer flag value and a vendor name. If
6972 the flag value is 0, the file is compatible with other toolchains. If it is 1,
6973 then the file is only compatible with the named toolchain. If it is greater
6974 than 1, the file can only be processed by other toolchains under some private
6975 arrangement indicated by the flag value and the vendor name.
6978 @subsection MIPS Attributes
6981 @item Tag_GNU_MIPS_ABI_FP (4)
6982 The floating-point ABI used by this object file. The value will be:
6986 0 for files not affected by the floating-point ABI.
6988 1 for files using the hardware floating-point with a standard double-precision
6991 2 for files using the hardware floating-point ABI with a single-precision FPU.
6993 3 for files using the software floating-point ABI.
6995 4 for files using the hardware floating-point ABI with 64-bit wide
6996 double-precision floating-point registers and 32-bit wide general
7001 @subsection PowerPC Attributes
7004 @item Tag_GNU_Power_ABI_FP (4)
7005 The floating-point ABI used by this object file. The value will be:
7009 0 for files not affected by the floating-point ABI.
7011 1 for files using double-precision hardware floating-point ABI.
7013 2 for files using the software floating-point ABI.
7015 3 for files using single-precision hardware floating-point ABI.
7018 @item Tag_GNU_Power_ABI_Vector (8)
7019 The vector ABI used by this object file. The value will be:
7023 0 for files not affected by the vector ABI.
7025 1 for files using general purpose registers to pass vectors.
7027 2 for files using AltiVec registers to pass vectors.
7029 3 for files using SPE registers to pass vectors.
7033 @node Defining New Object Attributes
7034 @section Defining New Object Attributes
7036 If you want to define a new @sc{gnu} object attribute, here are the places you
7037 will need to modify. New attributes should be discussed on the @samp{binutils}
7042 This manual, which is the official register of attributes.
7044 The header for your architecture @file{include/elf}, to define the tag.
7046 The @file{bfd} support file for your architecture, to merge the attribute
7047 and issue any appropriate link warnings.
7049 Test cases in @file{ld/testsuite} for merging and link warnings.
7051 @file{binutils/readelf.c} to display your attribute.
7053 GCC, if you want the compiler to mark the attribute automatically.
7059 @node Machine Dependencies
7060 @chapter Machine Dependent Features
7062 @cindex machine dependencies
7063 The machine instruction sets are (almost by definition) different on
7064 each machine where @command{@value{AS}} runs. Floating point representations
7065 vary as well, and @command{@value{AS}} often supports a few additional
7066 directives or command-line options for compatibility with other
7067 assemblers on a particular platform. Finally, some versions of
7068 @command{@value{AS}} support special pseudo-instructions for branch
7071 This chapter discusses most of these differences, though it does not
7072 include details on any machine's instruction set. For details on that
7073 subject, see the hardware manufacturer's manual.
7077 * AArch64-Dependent:: AArch64 Dependent Features
7080 * Alpha-Dependent:: Alpha Dependent Features
7083 * ARC-Dependent:: ARC Dependent Features
7086 * ARM-Dependent:: ARM Dependent Features
7089 * AVR-Dependent:: AVR Dependent Features
7092 * Blackfin-Dependent:: Blackfin Dependent Features
7095 * CR16-Dependent:: CR16 Dependent Features
7098 * CRIS-Dependent:: CRIS Dependent Features
7101 * D10V-Dependent:: D10V Dependent Features
7104 * D30V-Dependent:: D30V Dependent Features
7107 * Epiphany-Dependent:: EPIPHANY Dependent Features
7110 * H8/300-Dependent:: Renesas H8/300 Dependent Features
7113 * HPPA-Dependent:: HPPA Dependent Features
7116 * ESA/390-Dependent:: IBM ESA/390 Dependent Features
7119 * i386-Dependent:: Intel 80386 and AMD x86-64 Dependent Features
7122 * i860-Dependent:: Intel 80860 Dependent Features
7125 * i960-Dependent:: Intel 80960 Dependent Features
7128 * IA-64-Dependent:: Intel IA-64 Dependent Features
7131 * IP2K-Dependent:: IP2K Dependent Features
7134 * LM32-Dependent:: LM32 Dependent Features
7137 * M32C-Dependent:: M32C Dependent Features
7140 * M32R-Dependent:: M32R Dependent Features
7143 * M68K-Dependent:: M680x0 Dependent Features
7146 * M68HC11-Dependent:: M68HC11 and 68HC12 Dependent Features
7149 * Meta-Dependent :: Meta Dependent Features
7152 * MicroBlaze-Dependent:: MICROBLAZE Dependent Features
7155 * MIPS-Dependent:: MIPS Dependent Features
7158 * MMIX-Dependent:: MMIX Dependent Features
7161 * MSP430-Dependent:: MSP430 Dependent Features
7164 * NDS32-Dependent:: Andes NDS32 Dependent Features
7167 * NiosII-Dependent:: Altera Nios II Dependent Features
7170 * NS32K-Dependent:: NS32K Dependent Features
7173 * SH-Dependent:: Renesas / SuperH SH Dependent Features
7174 * SH64-Dependent:: SuperH SH64 Dependent Features
7177 * PDP-11-Dependent:: PDP-11 Dependent Features
7180 * PJ-Dependent:: picoJava Dependent Features
7183 * PPC-Dependent:: PowerPC Dependent Features
7186 * RL78-Dependent:: RL78 Dependent Features
7189 * RX-Dependent:: RX Dependent Features
7192 * S/390-Dependent:: IBM S/390 Dependent Features
7195 * SCORE-Dependent:: SCORE Dependent Features
7198 * Sparc-Dependent:: SPARC Dependent Features
7201 * TIC54X-Dependent:: TI TMS320C54x Dependent Features
7204 * TIC6X-Dependent :: TI TMS320C6x Dependent Features
7207 * TILE-Gx-Dependent :: Tilera TILE-Gx Dependent Features
7210 * TILEPro-Dependent :: Tilera TILEPro Dependent Features
7213 * V850-Dependent:: V850 Dependent Features
7216 * XGATE-Dependent:: XGATE Features
7219 * XSTORMY16-Dependent:: XStormy16 Dependent Features
7222 * Xtensa-Dependent:: Xtensa Dependent Features
7225 * Z80-Dependent:: Z80 Dependent Features
7228 * Z8000-Dependent:: Z8000 Dependent Features
7231 * Vax-Dependent:: VAX Dependent Features
7238 @c The following major nodes are *sections* in the GENERIC version, *chapters*
7239 @c in single-cpu versions. This is mainly achieved by @lowersections. There is a
7240 @c peculiarity: to preserve cross-references, there must be a node called
7241 @c "Machine Dependencies". Hence the conditional nodenames in each
7242 @c major node below. Node defaulting in makeinfo requires adjacency of
7243 @c node and sectioning commands; hence the repetition of @chapter BLAH
7244 @c in both conditional blocks.
7247 @include c-aarch64.texi
7251 @include c-alpha.texi
7267 @include c-bfin.texi
7271 @include c-cr16.texi
7275 @include c-cris.texi
7280 @node Machine Dependencies
7281 @chapter Machine Dependent Features
7283 The machine instruction sets are different on each Renesas chip family,
7284 and there are also some syntax differences among the families. This
7285 chapter describes the specific @command{@value{AS}} features for each
7289 * H8/300-Dependent:: Renesas H8/300 Dependent Features
7290 * SH-Dependent:: Renesas SH Dependent Features
7297 @include c-d10v.texi
7301 @include c-d30v.texi
7305 @include c-epiphany.texi
7309 @include c-h8300.texi
7313 @include c-hppa.texi
7317 @include c-i370.texi
7321 @include c-i386.texi
7325 @include c-i860.texi
7329 @include c-i960.texi
7333 @include c-ia64.texi
7337 @include c-ip2k.texi
7341 @include c-lm32.texi
7345 @include c-m32c.texi
7349 @include c-m32r.texi
7353 @include c-m68k.texi
7357 @include c-m68hc11.texi
7361 @include c-metag.texi
7365 @include c-microblaze.texi
7369 @include c-mips.texi
7373 @include c-mmix.texi
7377 @include c-msp430.texi
7381 @include c-nds32.texi
7385 @include c-nios2.texi
7389 @include c-ns32k.texi
7393 @include c-pdp11.texi
7405 @include c-rl78.texi
7413 @include c-s390.texi
7417 @include c-score.texi
7422 @include c-sh64.texi
7426 @include c-sparc.texi
7430 @include c-tic54x.texi
7434 @include c-tic6x.texi
7438 @include c-tilegx.texi
7442 @include c-tilepro.texi
7458 @include c-v850.texi
7462 @include c-xgate.texi
7466 @include c-xstormy16.texi
7470 @include c-xtensa.texi
7474 @c reverse effect of @down at top of generic Machine-Dep chapter
7478 @node Reporting Bugs
7479 @chapter Reporting Bugs
7480 @cindex bugs in assembler
7481 @cindex reporting bugs in assembler
7483 Your bug reports play an essential role in making @command{@value{AS}} reliable.
7485 Reporting a bug may help you by bringing a solution to your problem, or it may
7486 not. But in any case the principal function of a bug report is to help the
7487 entire community by making the next version of @command{@value{AS}} work better.
7488 Bug reports are your contribution to the maintenance of @command{@value{AS}}.
7490 In order for a bug report to serve its purpose, you must include the
7491 information that enables us to fix the bug.
7494 * Bug Criteria:: Have you found a bug?
7495 * Bug Reporting:: How to report bugs
7499 @section Have You Found a Bug?
7500 @cindex bug criteria
7502 If you are not sure whether you have found a bug, here are some guidelines:
7505 @cindex fatal signal
7506 @cindex assembler crash
7507 @cindex crash of assembler
7509 If the assembler gets a fatal signal, for any input whatever, that is a
7510 @command{@value{AS}} bug. Reliable assemblers never crash.
7512 @cindex error on valid input
7514 If @command{@value{AS}} produces an error message for valid input, that is a bug.
7516 @cindex invalid input
7518 If @command{@value{AS}} does not produce an error message for invalid input, that
7519 is a bug. However, you should note that your idea of ``invalid input'' might
7520 be our idea of ``an extension'' or ``support for traditional practice''.
7523 If you are an experienced user of assemblers, your suggestions for improvement
7524 of @command{@value{AS}} are welcome in any case.
7528 @section How to Report Bugs
7530 @cindex assembler bugs, reporting
7532 A number of companies and individuals offer support for @sc{gnu} products. If
7533 you obtained @command{@value{AS}} from a support organization, we recommend you
7534 contact that organization first.
7536 You can find contact information for many support companies and
7537 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
7541 In any event, we also recommend that you send bug reports for @command{@value{AS}}
7545 The fundamental principle of reporting bugs usefully is this:
7546 @strong{report all the facts}. If you are not sure whether to state a
7547 fact or leave it out, state it!
7549 Often people omit facts because they think they know what causes the problem
7550 and assume that some details do not matter. Thus, you might assume that the
7551 name of a symbol you use in an example does not matter. Well, probably it does
7552 not, but one cannot be sure. Perhaps the bug is a stray memory reference which
7553 happens to fetch from the location where that name is stored in memory;
7554 perhaps, if the name were different, the contents of that location would fool
7555 the assembler into doing the right thing despite the bug. Play it safe and
7556 give a specific, complete example. That is the easiest thing for you to do,
7557 and the most helpful.
7559 Keep in mind that the purpose of a bug report is to enable us to fix the bug if
7560 it is new to us. Therefore, always write your bug reports on the assumption
7561 that the bug has not been reported previously.
7563 Sometimes people give a few sketchy facts and ask, ``Does this ring a
7564 bell?'' This cannot help us fix a bug, so it is basically useless. We
7565 respond by asking for enough details to enable us to investigate.
7566 You might as well expedite matters by sending them to begin with.
7568 To enable us to fix the bug, you should include all these things:
7572 The version of @command{@value{AS}}. @command{@value{AS}} announces it if you start
7573 it with the @samp{--version} argument.
7575 Without this, we will not know whether there is any point in looking for
7576 the bug in the current version of @command{@value{AS}}.
7579 Any patches you may have applied to the @command{@value{AS}} source.
7582 The type of machine you are using, and the operating system name and
7586 What compiler (and its version) was used to compile @command{@value{AS}}---e.g.
7590 The command arguments you gave the assembler to assemble your example and
7591 observe the bug. To guarantee you will not omit something important, list them
7592 all. A copy of the Makefile (or the output from make) is sufficient.
7594 If we were to try to guess the arguments, we would probably guess wrong
7595 and then we might not encounter the bug.
7598 A complete input file that will reproduce the bug. If the bug is observed when
7599 the assembler is invoked via a compiler, send the assembler source, not the
7600 high level language source. Most compilers will produce the assembler source
7601 when run with the @samp{-S} option. If you are using @code{@value{GCC}}, use
7602 the options @samp{-v --save-temps}; this will save the assembler source in a
7603 file with an extension of @file{.s}, and also show you exactly how
7604 @command{@value{AS}} is being run.
7607 A description of what behavior you observe that you believe is
7608 incorrect. For example, ``It gets a fatal signal.''
7610 Of course, if the bug is that @command{@value{AS}} gets a fatal signal, then we
7611 will certainly notice it. But if the bug is incorrect output, we might not
7612 notice unless it is glaringly wrong. You might as well not give us a chance to
7615 Even if the problem you experience is a fatal signal, you should still say so
7616 explicitly. Suppose something strange is going on, such as, your copy of
7617 @command{@value{AS}} is out of sync, or you have encountered a bug in the C
7618 library on your system. (This has happened!) Your copy might crash and ours
7619 would not. If you told us to expect a crash, then when ours fails to crash, we
7620 would know that the bug was not happening for us. If you had not told us to
7621 expect a crash, then we would not be able to draw any conclusion from our
7625 If you wish to suggest changes to the @command{@value{AS}} source, send us context
7626 diffs, as generated by @code{diff} with the @samp{-u}, @samp{-c}, or @samp{-p}
7627 option. Always send diffs from the old file to the new file. If you even
7628 discuss something in the @command{@value{AS}} source, refer to it by context, not
7631 The line numbers in our development sources will not match those in your
7632 sources. Your line numbers would convey no useful information to us.
7635 Here are some things that are not necessary:
7639 A description of the envelope of the bug.
7641 Often people who encounter a bug spend a lot of time investigating
7642 which changes to the input file will make the bug go away and which
7643 changes will not affect it.
7645 This is often time consuming and not very useful, because the way we
7646 will find the bug is by running a single example under the debugger
7647 with breakpoints, not by pure deduction from a series of examples.
7648 We recommend that you save your time for something else.
7650 Of course, if you can find a simpler example to report @emph{instead}
7651 of the original one, that is a convenience for us. Errors in the
7652 output will be easier to spot, running under the debugger will take
7653 less time, and so on.
7655 However, simplification is not vital; if you do not want to do this,
7656 report the bug anyway and send us the entire test case you used.
7659 A patch for the bug.
7661 A patch for the bug does help us if it is a good one. But do not omit
7662 the necessary information, such as the test case, on the assumption that
7663 a patch is all we need. We might see problems with your patch and decide
7664 to fix the problem another way, or we might not understand it at all.
7666 Sometimes with a program as complicated as @command{@value{AS}} it is very hard to
7667 construct an example that will make the program follow a certain path through
7668 the code. If you do not send us the example, we will not be able to construct
7669 one, so we will not be able to verify that the bug is fixed.
7671 And if we cannot understand what bug you are trying to fix, or why your
7672 patch should be an improvement, we will not install it. A test case will
7673 help us to understand.
7676 A guess about what the bug is or what it depends on.
7678 Such guesses are usually wrong. Even we cannot guess right about such
7679 things without first using the debugger to find the facts.
7682 @node Acknowledgements
7683 @chapter Acknowledgements
7685 If you have contributed to GAS and your name isn't listed here,
7686 it is not meant as a slight. We just don't know about it. Send mail to the
7687 maintainer, and we'll correct the situation. Currently
7689 the maintainer is Nick Clifton (email address @code{nickc@@redhat.com}).
7691 Dean Elsner wrote the original @sc{gnu} assembler for the VAX.@footnote{Any
7694 Jay Fenlason maintained GAS for a while, adding support for GDB-specific debug
7695 information and the 68k series machines, most of the preprocessing pass, and
7696 extensive changes in @file{messages.c}, @file{input-file.c}, @file{write.c}.
7698 K. Richard Pixley maintained GAS for a while, adding various enhancements and
7699 many bug fixes, including merging support for several processors, breaking GAS
7700 up to handle multiple object file format back ends (including heavy rewrite,
7701 testing, an integration of the coff and b.out back ends), adding configuration
7702 including heavy testing and verification of cross assemblers and file splits
7703 and renaming, converted GAS to strictly ANSI C including full prototypes, added
7704 support for m680[34]0 and cpu32, did considerable work on i960 including a COFF
7705 port (including considerable amounts of reverse engineering), a SPARC opcode
7706 file rewrite, DECstation, rs6000, and hp300hpux host ports, updated ``know''
7707 assertions and made them work, much other reorganization, cleanup, and lint.
7709 Ken Raeburn wrote the high-level BFD interface code to replace most of the code
7710 in format-specific I/O modules.
7712 The original VMS support was contributed by David L. Kashtan. Eric Youngdale
7713 has done much work with it since.
7715 The Intel 80386 machine description was written by Eliot Dresselhaus.
7717 Minh Tran-Le at IntelliCorp contributed some AIX 386 support.
7719 The Motorola 88k machine description was contributed by Devon Bowen of Buffalo
7720 University and Torbjorn Granlund of the Swedish Institute of Computer Science.
7722 Keith Knowles at the Open Software Foundation wrote the original MIPS back end
7723 (@file{tc-mips.c}, @file{tc-mips.h}), and contributed Rose format support
7724 (which hasn't been merged in yet). Ralph Campbell worked with the MIPS code to
7725 support a.out format.
7727 Support for the Zilog Z8k and Renesas H8/300 processors (tc-z8k,
7728 tc-h8300), and IEEE 695 object file format (obj-ieee), was written by
7729 Steve Chamberlain of Cygnus Support. Steve also modified the COFF back end to
7730 use BFD for some low-level operations, for use with the H8/300 and AMD 29k
7733 John Gilmore built the AMD 29000 support, added @code{.include} support, and
7734 simplified the configuration of which versions accept which directives. He
7735 updated the 68k machine description so that Motorola's opcodes always produced
7736 fixed-size instructions (e.g., @code{jsr}), while synthetic instructions
7737 remained shrinkable (@code{jbsr}). John fixed many bugs, including true tested
7738 cross-compilation support, and one bug in relaxation that took a week and
7739 required the proverbial one-bit fix.
7741 Ian Lance Taylor of Cygnus Support merged the Motorola and MIT syntax for the
7742 68k, completed support for some COFF targets (68k, i386 SVR3, and SCO Unix),
7743 added support for MIPS ECOFF and ELF targets, wrote the initial RS/6000 and
7744 PowerPC assembler, and made a few other minor patches.
7746 Steve Chamberlain made GAS able to generate listings.
7748 Hewlett-Packard contributed support for the HP9000/300.
7750 Jeff Law wrote GAS and BFD support for the native HPPA object format (SOM)
7751 along with a fairly extensive HPPA testsuite (for both SOM and ELF object
7752 formats). This work was supported by both the Center for Software Science at
7753 the University of Utah and Cygnus Support.
7755 Support for ELF format files has been worked on by Mark Eichin of Cygnus
7756 Support (original, incomplete implementation for SPARC), Pete Hoogenboom and
7757 Jeff Law at the University of Utah (HPPA mainly), Michael Meissner of the Open
7758 Software Foundation (i386 mainly), and Ken Raeburn of Cygnus Support (sparc,
7759 and some initial 64-bit support).
7761 Linas Vepstas added GAS support for the ESA/390 ``IBM 370'' architecture.
7763 Richard Henderson rewrote the Alpha assembler. Klaus Kaempf wrote GAS and BFD
7764 support for openVMS/Alpha.
7766 Timothy Wall, Michael Hayes, and Greg Smart contributed to the various tic*
7769 David Heine, Sterling Augustine, Bob Wilson and John Ruttenberg from Tensilica,
7770 Inc.@: added support for Xtensa processors.
7772 Several engineers at Cygnus Support have also provided many small bug fixes and
7773 configuration enhancements.
7775 Jon Beniston added support for the Lattice Mico32 architecture.
7777 Many others have contributed large or small bugfixes and enhancements. If
7778 you have contributed significant work and are not mentioned on this list, and
7779 want to be, let us know. Some of the history has been lost; we are not
7780 intentionally leaving anyone out.
7782 @node GNU Free Documentation License
7783 @appendix GNU Free Documentation License
7787 @unnumbered AS Index
projects / deliverable / binutils-gdb.git / blob